Many thanks for the quick reply. I have tried this, but I'm still getting
errors. The two columns are in another worksheet - would this make a
difference?

I assume that the '--' in the formula are dashes

"Elkar" wrote:

Use SUMPRODUCT if you have more than one condition to check.

=SUMPRODUCT(--(A1:A100=1),--(B1:B100="Yes"))

HTH,
Elkar


"tonefbr" wrote:

I would like to sum all occurences of a value in Column A, if another value
occurs in column B in the same row... but I cant figure out how to do it.
Essentially I want to calculate 'How many times does Column A = 1 when Column
B = Yes'? Any help would be most appreciated.