I have an excel 2007 spreadsheet that has last month's data and this month's data.

Last month's serial numbers are posted in Column A, this month's SNs are in Column X. Other columns contain names, addresses, etc... Serial numbers are unique by person.

I've tried a couple of formulas, but don't seem to get any errors or answers -- the cell where formula is entered just shows the formula I typed in.

Formulas I've tried so far:

=ISNA(MATCH(A2,X2:X404,TRUE))

=VLOOKUP(A2,A2:X404,24,FALSE)

I feel like I must be missing something really obvious... Column A has data in rows 2-378, column X has data in rows 2-402.

I'd like to know what's in column A that is NOT in column X and vice versa.

Thanks for your help!