I did forget to mention I am not very good at VBA.
Let A1:B17 house the data, headers included...
<TABLE style="WIDTH: 185pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=247 x:str><COLGROUP><COL style="WIDTH: 89pt; mso-width-source: userset; mso-width-alt: 4352" width=119><COL style="WIDTH: 48pt" span=2 width=64><TBODY><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; WIDTH: 89pt; HEIGHT: 12.75pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 height=17 width=119>
Information Date</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 width=64>
Amount</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 width=64>
Average</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39814">
1/1/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
5</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B2)>=10,AVERAGE(INDEX($B$2:B2,LARGE(IF($B$2:B2<>"",ROW($B$2:B2)-ROW($B$2)+1),10)):B2),"")' x:arrayrange="C2"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39815">
1/2/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
5</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B3)>=10,AVERAGE(INDEX($B$2:B3,LARGE(IF($B$2:B3<>"",ROW($B$2:B3)-ROW($B$2)+1),10)):B3),"")' x:arrayrange="C3"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39816">
1/3/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
9</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B4)>=10,AVERAGE(INDEX($B$2:B4,LARGE(IF($B$2:B4<>"",ROW($B$2:B4)-ROW($B$2)+1),10)):B4),"")' x:arrayrange="C4"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39817">
1/4/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
3</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B5)>=10,AVERAGE(INDEX($B$2:B5,LARGE(IF($B$2:B5<>"",ROW($B$2:B5)-ROW($B$2)+1),10)):B5),"")' x:arrayrange="C5"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39818">
1/5/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
4</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B6)>=10,AVERAGE(INDEX($B$2:B6,LARGE(IF($B$2:B6<>"",ROW($B$2:B6)-ROW($B$2)+1),10)):B6),"")' x:arrayrange="C6"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39819">
1/6/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22> </TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B7)>=10,AVERAGE(INDEX($B$2:B7,LARGE(IF($B$2:B7<>"",ROW($B$2:B7)-ROW($B$2)+1),10)):B7),"")' x:arrayrange="C7"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39820">
1/7/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
9</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B8)>=10,AVERAGE(INDEX($B$2:B8,LARGE(IF($B$2:B8<>"",ROW($B$2:B8)-ROW($B$2)+1),10)):B8),"")' x:arrayrange="C8"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39821">
1/8/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
3</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B9)>=10,AVERAGE(INDEX($B$2:B9,LARGE(IF($B$2:B9<>"",ROW($B$2:B9)-ROW($B$2)+1),10)):B9),"")' x:arrayrange="C9"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39822">
1/9/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
2</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B10)>=10,AVERAGE(INDEX($B$2:B10,LARGE(IF($B$2:B10<>"",ROW($B$2:B10)-ROW($B$2)+1),10)):B10),"")' x:arrayrange="C10"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39823">
1/10/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
8</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 x:str="" x:fmla='=IF(COUNT($B$2:B11)>=10,AVERAGE(INDEX($B$2:B11,LARGE(IF($B$2:B11<>"",ROW($B$2:B11)-ROW($B$2)+1),10)):B11),"")' x:arrayrange="C11"> </TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39824">
1/11/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" id=td_post_2154733 class=xl22 align=right x:num>
9</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B12)>=10,AVERAGE(INDEX($B$2:B12,LARGE(IF($B$2:B12<>"",ROW($B$2:B12)-ROW($B$2)+1),10)):B12),"")' x:arrayrange="C12">
5.7</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39825">
1/12/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
5</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B13)>=10,AVERAGE(INDEX($B$2:B13,LARGE(IF($B$2:B13<>"",ROW($B$2:B13)-ROW($B$2)+1),10)):B13),"")' x:arrayrange="C13">
5.7</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39826">
1/13/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
7</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B14)>=10,AVERAGE(INDEX($B$2:B14,LARGE(IF($B$2:B14<>"",ROW($B$2:B14)-ROW($B$2)+1),10)):B14),"")' x:arrayrange="C14">
5.9</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39827">
1/14/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22> </TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B15)>=10,AVERAGE(INDEX($B$2:B15,LARGE(IF($B$2:B15<>"",ROW($B$2:B15)-ROW($B$2)+1),10)):B15),"")' x:arrayrange="C15">
5.9</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39828">
1/15/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num>
8</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B16)>=10,AVERAGE(INDEX($B$2:B16,LARGE(IF($B$2:B16<>"",ROW($B$2:B16)-ROW($B$2)+1),10)):B16),"")' x:arrayrange="C16">
5.8</TD></TR><TR style="HEIGHT: 12.75pt" height=17><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 12.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl23 height=17 align=right x:num="39829">
1/16/2009</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22> </TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl22 align=right x:num x:fmla='=IF(COUNT($B$2:B17)>=10,AVERAGE(INDEX($B$2:B17,LARGE(IF($B$2:B17<>"",ROW($B$2:B17)-ROW($B$2)+1),10)):B17),"")' x:arrayrange="C17">
5.8</TD></TR></TBODY></TABLE>
C2:
Control+shift+enter, not just enter...
Code:
=IF(COUNT($B$2:B2)>=10,AVERAGE(INDEX($B$2:B2,
LARGE(IF($B$2:B2<>"",ROW($B$2:B2)-ROW($B$2)+1),10)):B2),"")
and copy down.