Hello all,

I need help with a validation? problem.

I have a spreadsheet with following columns:

Column A: user ID (Number). Can contain duplicate entries of single user.
Column B: "Add", "Remove" drop-down column. Drop-down set using data validation.

What I need is if value in Column B is changed and user ID is a duplicate number to get a information message that we are changing a value of duplicate entry (see below for example).

In below example I would get information message only when column "Add/Remove" for entries 2 and 4 are changed (red ones) Because for these 2 entries User ID is same (same user).

User ID Add/Remove
1 123 Add
2 234 Remove
3 345 Add
4 234 Add
5 456 Remove
6 789 Add

P.S. VBA code solution is OK for me as well.

Thank you in advance & kind regards,
Marko