Ok thanks! Also, I just wanted to check. When I use this
=SUMPRODUCT((ISNUMBER(Y!$1:$3))*(Y!$1:$3<=Z!A1)*(X!$B$1:$B$3="T"))
and I drag the fill handle downwards. Each count also includes those from the count preceding it right?
That is:
In order to find the count in a particular class, I would have to subtract the count from the one before it.
I think I have answered by own question.
So, I presume that if I want the total of ALL cells in "Y" who have a corresponding "T" in "X" in their respective row designations I would leave off the middle condition.
So
Total =SUMPRODUCT((ISNUMBER(Y!$1:$3))*(X!$B$1:$B$3="T"))