Multiple vlookup formula won't work if expanded to 4 vlookups

hi everyone,

I have the following formula:

=IF(ISNA(VLOOKUP(A16&"-01",'Data Month 1'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 2'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 3'!W:W,1,0)),"",VLOOKUP(A16&"-01",'Data Month 3'!W:W,1,0)),VLOOKUP(A16&"-01",'Data Month 2'!W:W,1,0)),VLOOKUP(A16&"-01",'Data Month 1'!W:W,1,0))

This formula works just fine. However, when I try to add another worksheet Data Month 4:

=IF(ISNA(VLOOKUP(A16&"-01",'Data Month 1'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 2'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 3'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 4'!W:W,1,0)),"",VLOOKUP(A16&"-01",'Data Month 3'!W:W,1,0)),VLOOKUP(A16&"-01",'Data Month 2'!W:W,1,0)),VLOOKUP(A16&"-01",'Data Month 1'!W:W,1,0)),IF(ISNA(VLOOKUP(A16&"-01",'Data Month 4'!W:W,1,0))

I get a message that I'm missing a parenthesis. I've tried a number of combinations but I haven't been able to figure it out. Any ideas?

thanks!

Nevermind. Figured it out. I'm stupid. Thanks.