Yes it does. Hmm. I amstill trying to understand this, so that I can change it as needed.

So, in this case, the function SUMPRODUCT only has ONE argument right?

And that argument is just whatever the result of 

(ISNUMBER(Y!$1:$3))*(Y!$1:$3<=Z!A1)*(X!$B$1:$B$3="T")
is,correct?

If so, I have 2 more quick questions. But I will wait first.