Not sure why, but the "faster" one didn't work. I still got a value of zero.
Thankfully, the original function (sumproduct) worked exactly like I hoped.
Thank you both for your willingness to help.

"Harlan Grove" wrote:

"T. Valko" wrote...
Try this:

=SUMPRODUCT(--(ISNUMBER(MATCH(Sheet2!C1:C100,ID,0))))
....

If recalc speed isn't essential,

=SUMPRODUCT(COUNTIF(ID,Sheet2!C1:C100))

should return the same result. If recalc speed is essential, I believe the
array formula

=COUNT(MATCH(Sheet2!C1:C100,ID,0))

would be faster.