In versions of XL prior to 2007 you can't use full-column references
with SUMPRODUCT, so try it like this:

=SUMPRODUCT((A2:A1000=A1)*(B2:B1000=B1)*(C2:C1000) )

I've assumed 1000 rows - adjust to suit.

Hope this helps.

Pete

On Apr 21, 4:40*pm, krandall
wrote:
I need a formula to add a column based on 2 criteria.

If A:A = A1 and B:B = B1 then sum C:C