Jacob Skaria wrote...
Replace Book1, Sheet1 and Sheet2 to suit your requirement

=COUNTIF([Book1]Sheet1!$A:$A,A2)+COUNTIF([Book1]Sheet2!$A:$A,A2)
....

Problem is that COUNTIF would return #REF! if the referenced workbook
(s) is(are) closed. When working with external references, best to use
SUMPRODUCT rather than either COUNTIF or SUMIF.

That said, if all one wants to do is count, and if the range(s) to be
counted is(are) all numbers and the criteria, A2, is also a number,
then you could use a single FREQUENCY call.

=INDEX(FREQUENCY('X:\y\[z.xls]Sheet1:Sheet2'!$A:$A,A2*
{0.999999999999999;1}),2)

FREQUENCY, unlike COUNTIF, does handle external references into closed
workbooks.