>>For Michel, where he's trying to trap for occurences that happen more quickly than code can trap, using the data engine by forcing it to validate values thru a candidate key will ensure that no duplicates will be stored. So, if that's the best approach for him, there's a ready solution to address the "leakage."
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>Yup, it's what I decided to apply. See my other reply which the full sample which explains clearly the situation.

Glad to hear you found a solution.

Jay