Try something like this:

In WB2 assume customer numbers are in the range Sheet1 A1:A10.
In WB1 assume customer numbers are in the range Sheet1 A1:A10.

In WB2 Sheet1 enter this formula in B1. A result of "X" means the customer
number *is not* in WB1.

=IF(COUNT(MATCH(A1,[WB1.xls]Sheet1!$A$1:$A$10,0)),"","X")



--
Biff
Microsoft Excel MVP


"Kathy" wrote in message
...
I am new to the VLOOKUP function and I am told that it can do this.

I need to compare two columns of data and find what is new in one of the
columns.

The data is in two separate workbooks, although I could put them in one
workbook if it will facilitate the formula.

So for instance, in workbook (WB) 1, I have a column for customer number
with a bunch of data and in WB2, I have a column for customer number with
a
bunch of data. I just want to compare the two customer number columns to
each
other and find any new customer numbers added in WB2 that are not in WB1
for
instance.

I tried and couldn't get the formula to work.

Thanks,
--
Kathy