You could have a contruct like:

=IF(ISNA(VLOOKUP(first_sheet_formula)),
IF(ISNA(VLOOKUP(second_sheet_formula)),"Not
Present",VLOOKUP(second_sheet_formula)),VLOOKUP(fi rst_sheet_formula))

You could extend this for more sheets, but the formula will become a
bit unwieldy.

Hope this helps.

Pete