>When adding a duplicate key in a table with a primary index, VFP generates a canned message, something like "Cannot update table. Uniqueness of index is violated.", or something like that. How can I customize this message. This should be easy!

This is easy if you usse table buffering. Then VFP won't throw an error message, the TABLEUPDATE command will fail. Just check the results of TABLEUPDATE, and if they are false, check the contents of AERROR to see if it was a trigger or whatever, and deal with it.