I have a formula i'm using in excel 2007 and it works just fine. But the problem is when I open it in 2003 it works ok from that start but as soon as I do anything to the data in gives me a NAME error. Anyone have any insight as to why. Or suggestion as to how I could reformulate?

{=IF(ISNA(INDEX('New Dates'!$A$1:$C$800,MATCH(A7&B7,'New Dates'!A:A&'New Dates'!B:B,0),3)),"",INDEX('New Dates'!$A$1:$C$800,MATCH(A7&B7,'New Dates'!A:A&'New Dates'!B:B,0),3))}