Quote Originally Posted by xld

Dont' you mean

=SUMPRODUCT((ISNUMBER('Cold Difference'!$A$1:$IV$4))*('Cold Difference'!$A$1:$IV$4<=Charts!A1)
*(ISNUMBER(MATCH('Cooling Type'!$A$1:$A$4,{"C","K"},0)))*('Cooling Type'!$B$1:$B$4="T"))
I am not sure what you are doing with the 'MATCH' as I have never used it. DO I need it? (presuming I don't care about neatness for now)

I am not sure what part of my
=SUMPRODUCT((ISNUMBER( 'Cold Difference'!$1:$4))*('Cold Difference'!$1:$4<=Charts!A1)* ... ... (('Cooling Type'!$A$1:$A$4="C")*('Cooling Type'!$B$1:$B$4="T")))
in particular you are correcting? Could you maybe boldface it?

I have the condition:
(ISNUMBER( 'Cold Difference'!$1:$4))
ANDed with the condition

('Cold Difference'!$1:$4<=Charts!A1)
ANDed with the resultant of the two conditions

(('Cooling Type'!$A$1:$A$4="C")*('Cooling Type'!$B$1:$B$4="T"))
Updated sample file attached. You can see that on the "Charts" sheet, everything works out.