In article ,
TARS1 wrote:

...determine how may times 'XX' or 'YY' occurs in column A?

Try...

=SUMPRODUCT(--(ISNUMBER(MATCH(A1:A100,{"XX","YY"},0))))

or

=SUMPRODUCT(--(ISNUMBER(MATCH(A1:A100,B1:B2,0))))

....where B1 contains your first criterion, such as XX, and B2 contains
your second criterion, such as YY.

Hope this helps!