How to prevent duplicate value in one field checking it from two or more fields

[inder]

I have two fields Phone1 and Phone2 in my form. I want Phone1 after update to check its duplicate value in both phone1 and phone2.
Similarly Phone2 to check phone2's duplicate value in both phone1 and phone2 and find that record in database and show it to me.

[Seth Schrock]

This is why you normalize your database. It makes this problem disappear. See Database Normalization and Table Structures.

Are you wanting them to be checked in the whole database or just within the one record?