The "IF" function (see the part of spread sheet attached)or two formulas in one is it possible?

I am haveing some problems in resolving this one and no one I know can answer it for me. I have this formula in place working
=IF((OR(D7="",D6="")),0,IF((D7<D6),((D7-D6)*24)+24,(D7-D6)*24))
BUT I need to add the option of
=if("Lunch" is selected from drop box,the amount the above formula is for
will result in "0" instead.
<TABLE style="WIDTH: 131pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=174><COLGROUP><COL style="WIDTH: 83pt; mso-width-source: userset; mso-width-alt: 4022" width=110><COL style="WIDTH: 48pt; mso-width-source: userset; mso-width-alt: 2340" width=64><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: #ddd9c4; WIDTH: 83pt; HEIGHT: 15pt; BORDER-TOP: #f0f0f0; BORDER-RIGHT: #f0f0f0" class=xl67 height=20 width=110>DESCRIPTION</TD><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #f0f0f0; BORDER-RIGHT: #f0f0f0" width=64></TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: #b7dee8; HEIGHT: 15pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl68 height=20>Lunch</TD><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: transparent; BORDER-TOP: #f0f0f0; BORDER-RIGHT: #f0f0f0"><This is drop box</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: gray 0.5pt solid; BORDER-LEFT: gray 0.5pt solid; BACKGROUND-COLOR: #ffcc99; HEIGHT: 15pt; BORDER-TOP: gray 0.5pt solid; BORDER-RIGHT: gray 0.5pt solid" class=xl63 height=20>8:00 AM</TD><TD style="BORDER-BOTTOM: gray 0.5pt solid; BORDER-LEFT: gray; BACKGROUND-COLOR: #ffcc99; BORDER-TOP: gray 0.5pt solid; BORDER-RIGHT: gray 0.5pt solid" class=xl64> Total </TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: gray 0.5pt solid; BACKGROUND-COLOR: #ffcc99; HEIGHT: 15pt; BORDER-TOP: gray; BORDER-RIGHT: gray 0.5pt solid" class=xl65 height=20>9:30 AM</TD><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: gray; BACKGROUND-COLOR: #ffcc99; WIDTH: 48pt; BORDER-TOP: gray; BORDER-RIGHT: gray 0.5pt solid" class=xl66 width=64>1.50 </TD></TR></TBODY></TABLE> ^this is amount effected or where formula is