onthefritz wrote...
I have a spreadsheet that I would like to count the number of occurrences of
a particular value in one column that also have a particular value in another.

For instance, I want the number of times the value in column B = Yes when
the value in column C = 0.
....

No need to use additional supporting cells/ranges. Try something like

=SUMPRODUCT(--(B2:B1001="Yes"),--(C2:C1001=0))