try
=sumproduct(--('all books'!A1:A1000="Suzie Smith"),--(C1:C1000="Tuesday"))
the --( changes the logical true false to a numeric 1,0.

you cannot use (before 2007) the shorthand for the full column
A:A is a non-no.

"The BriGuy" wrote:

I am looking for a formula to count instances, from multiple sheets, where
criteria in one column and another column occur. For example I have 4
worksheets and I amd looking for all instances where column A in all books
=Suzie Smith AND where column C in all books = Tuesday. Any ideas?

Thanks