Hello I am currently trying to use Excel 2003 Data validation to prevent duplicate data Entry.

The data I have for example in A1:A4 is as follows

04-20-026-22W4/2
16-33-025-22W4/2
07-27-026-22W4/0
04-20-026-22W4/0

In the data validation I have custom and this for the formula

=COUNTIF($A$1:$A$4,A1)<=1 for cell A1

My problem arises in that I need it to do this lookup based on the wildcard for the last number.

So that cell A1 = A4 and therefore will not let me put in 04-20-026-22W4/0 or /2 or anything else.

So something similar to 04-20-026-22W4/* where * = wildcard.

The cells are currently formatted as General and I have tried a few variations of countif and sumproduct with no luck.

Thanks in advance for any help you can offer.