All (especially Frank Kabel, I guess)

I have done some googles on the newsgroup on the topic of SUMPRODUCT, and
frankly am a little flabberrgasted. So, could some pundit advise if the
following is possible, please?

I am using 3D sums (like =SUM(Sheet1:Sheet4!A1) to sum accross multiple
sheets. What I would like to use an array (1,1,1,0) which indicates whether
the values from a particular sheet are included in the sum, or not. Hence
the idea of using SUMPRODUCT, resulting web search, confusion, and newsgroup
question.

Any takers on this one?

Alex J