Thanks Bob! I've taken a look at your sample file and I can see what's
happening.

The reason why Biff and I are getting a #VALUE error is that we're
confirming the formula with CONTROL+SHIFT+ENTER.

My understanding is that the TRANSPOSE function needs to be confirmed
with CONTROL+SHIFT+ENTER, even when used within SUMPRODUCT.

Now, while your formula returns the correct answer as it stands, if
Sheet1!A1 contains 100 and Sheet2!A1 contains 10, the formula returns 0
which as you know would be incorrect.

Thanks again, Bob!

In article ,
Domenic wrote:

Bob,

Very interesting! Would you mind sending me a sample file? I'd really
appreciate it. Thanks!