In addition to Peo's suggestions, I believe if you download and install
the free add-in Morefunc.xll, you should be able to use the THREED
function...

=AVERAGE(IF(THREED('Sheet1:Sheet13'!B2)0,THREED(' Sheet1:Sheet13'!B2)))

....confirmed with CONTROL+SHIFT+ENTER. Note that I haven't been able to
test it since this add-in is not compatible with my Mac version of
Excel. If you'd like to try it, the add-in can be found at the
following link...

http://xcell05.free.fr/

Hope this helps!

In article ,
curtll wrote:

Not really wanting to do it that way. I already have the spreadsheet
the way I like it. I have the dates in the A column. Why cant I just
average 1 cell across multiple worksheets and not include zeros in the
calculation?