Quote Originally Posted by xld
=SUMPRODUCT((ISNUMBER(Y!$1:$3))*(Y!$1:$3<=Z!A1)*(ISNUMBER(MATCH(X!$B$1:$B$3 ,{"C","K"},0))))
OK. I used (Sheet Names Changed, Sorry)

=SUMPRODUCT((ISNUMBER('Cold Difference'!$1:$4))*('Cold Difference'!$1:$4<=Charts!A1)*(('Cooling Type'!$A$1:$A$4="C")+('Cooling Type'!$A$1:$A$4="K")))
and it seems to work. Sorry..."C" or "K" would be found in column "A" not "B"

it can't be C and K, if it is C it is NOT K and vice versa
Oops. I meant (Column A is a "C" or "K") AND (Column B is a "T")

for which I used 

=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")))
which also works fine.

Not pretty, but they work.