Try this...
Sheet1
<TABLE style="PADDING-RIGHT: 2pt; PADDING-LEFT: 2pt; FONT-SIZE: 10pt; FONT-FAMILY: Verdana,Arial; BACKGROUND-COLOR: #ffffff" cellSpacing=0 cellPadding=0 border=0><COLGROUP><COL style="FONT-WEIGHT: bold; WIDTH: 30px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 23px"><COL style="WIDTH: 33px"><COL style="WIDTH: 36px"><COL style="WIDTH: 29px"><COL style="WIDTH: 32px"><COL style="WIDTH: 29px"></COLGROUP><TBODY><TR style="FONT-WEIGHT: bold; FONT-SIZE: 8pt; BACKGROUND-COLOR: #cacaca; TEXT-ALIGN: center"><TD> </TD><TD>A</TD><TD>B</TD><TD>C</TD><TD>D</TD><TD>E</TD><TD>F</TD><TD>G</TD><TD>H</TD><TD>I</TD><TD>J</TD><TD>K</TD><TD>L</TD><TD>M</TD><TD>N</TD></TR><TR style="HEIGHT: 17px"><TD style="FONT-SIZE: 8pt; BACKGROUND-COLOR: #cacaca; TEXT-ALIGN: center">1</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT: #000000 1px solid; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M1</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M2</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M3</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M4</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M5</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M6</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M7</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M8</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M9</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M10</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD><TD style="BORDER-RIGHT: #000000 1px solid; BORDER-TOP: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD></TR><TR style="HEIGHT: 17px"><TD style="FONT-SIZE: 8pt; BACKGROUND-COLOR: #cacaca; TEXT-ALIGN: center">2</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT: #000000 1px solid; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">1</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">2</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">x</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">x</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">4</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">5</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">10</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">10</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">9</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">1</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M3</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M4</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD></TR><TR style="HEIGHT: 17px"><TD style="FONT-SIZE: 8pt; BACKGROUND-COLOR: #cacaca; TEXT-ALIGN: center">3</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT: #000000 1px solid; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">5</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">x</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">6</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">8</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">6</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">4</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">9</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">8</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">5</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">x</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M2</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">M10</TD><TD style="BORDER-TOP-WIDTH: 1px; BORDER-RIGHT: #000000 1px solid; BORDER-LEFT-WIDTH: 1px; BORDER-LEFT-COLOR: #000000; COLOR: #ffffff; BORDER-TOP-COLOR: #000000; BORDER-BOTTOM: #000000 1px solid; TEXT-ALIGN: center">_</TD></TR></TBODY></TABLE>
This array formula** entered in L2:
=IF(COLUMNS($L2:L2)>COUNTIF($A2:$J2,"x"),"",INDEX($1:$1,SMALL(IF($A2:$J2="x",COLUMN($A2:$J2)),COLUMNS($L2:L2))))
** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.
Copy down as needed then across until you get a column full of blanks.