Gridview Update with Unique Constraint Validation

I have a textbox in a gridview that contains an index value and must be unique. I have created a custom validator for the insert so that it checks to make sure the value does not exist in the database and this works fine. However, if I use the same custom validator in the gridview edit template, it will not let me update a row with the orginonal value because it sees that it is already in the database. How someone already solved this so I don't have to think to hard??? Thanks for the help. Earl  
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