Here is what I want the formula to do:
If the first VLookup arguement does not return any results, have another
VLookup formula look in another sheet. This is a simple example of the
formula:

=IF(ISNA(VLOOKUP(A1,A!$A$1:A!B3,2,FALSE),Vlookup(A 1,B!A1:B!B4,2,False),0))

Any help would be greatly appreciated.

Thanks. ME.