I have a sheet that averages numbers from another sheet (2007 Flk):

=AVERAGE('2007 Flk'!G4,'2007 Flk'!K4,'2007 Flk'!O4,'2007 Flk'!W4,'2007
Flk'!AA4,'2007 Flk'!AE4)

The problem is that "2007 Flk" has some DIV/0 errors in it. So I
tried the following formula but it didn't work:

=AVERAGE(IF(ISNUMBER('2007Flk'!G4,'2007Flk'!P4,'20 07Flk'!
AC4),'2007Flk'!G4,'2007Flk'!P4,'2007Flk'!AC4))

That formula/function seems to only work if it's not referencing
another sheet.

Can anyone help me get this formula to work?

Thanks.