Have you tried to use COUNTIF.3D?

On my version (5.06), which I have redownloaded to be sure I didn't miss
anything, COUNTIF.3D, although documented in HELP, does not exist.
--ron

Weird. It's there for me. Also 5.06, downloaded sometime this last
spring, IIRC. I tried it quick and it works. I put this on 2 sheets:
Start
Start
Stop
Stop
Start
Stop
Stop
Stop
Start

=COUNTIF.3D(Sheet1:Sheet2!A1:A9,"Stop")
Returns "10".

I don't know what to tell you. Corrupted download?