You could hard code it like:
<TABLE style="WIDTH: 377pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=502><COLGROUP><COL style="WIDTH: 377pt; mso-width-source: userset; mso-width-alt: 9179" width=502><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: #d7e4bc; WIDTH: 377pt; HEIGHT: 15pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl63 height=20 width=502>=IF(AND(OR(B31=900,B31=1800,B31=3600),F8>=10,F8<=12),70,"")
</TD></TR></TBODY></TABLE>
or use another cell to reference the value in B31, for example let c31 house the value you choose (900, 1800, 3600....)
like:
<TABLE style="WIDTH: 377pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=502><COLGROUP><COL style="WIDTH: 377pt; mso-width-source: userset; mso-width-alt: 9179" width=502><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: #d7e4bc; WIDTH: 377pt; HEIGHT: 15pt; BORDER-TOP: windowtext 0.5pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 height=20 width=502>=IF(AND(B31=C31,F8>=10,F8<=12),70,"")
</TD></TR></TBODY></TABLE>