The following is my formula, how do I get it return 0 instead of #N/A? I
tried

VLOOKUP(A17,'November 2007'!C$3:R$261,14,FALSE)+VLOOKUP(A18,'November
2007'!C$3:R$261,14,FALSE)+VLOOKUP(A20,'November
2007'!C$3:R$261,14,FALSE)+VLOOKUP(A21,'November 2007'!C$3:R$261,14,FALSE)

I tried using the following which did't give me the 0 instead #N/A but it
gave me the wrong amount. Maybe you can tell me where I went wrong.

IF(ISNA(VLOOKUP(A17,'November
2007'!C$3:R$261,14,FALSE)),"",VLOOKUP(A17,'Novembe r
2007'!C$3:R$261,14,FALSE)+IF(ISNA(VLOOKUP(A18,'Nov ember
2007'!C$3:R$261,14,FALSE)),VLOOKUP(A18,'November
2007'!C$3:R$261,14,FALSE)+IF(ISNA(VLOOKUP(A20,'Nov ember
2007'!C$3:R$261,14,FALSE)),VLOOKUP(A20,'November
2007'!C$3:R$261,14,FALSE)+IF(ISNA(VLOOKUP(A21,'Nov ember
2007'!C$3:R$261,14,FALSE)),VLOOKUP(A21,'November 2007'!C$3:R$261,14,FALSE)))))

Thanks in advance for your help.