Hi Claude,

>Even if user UPDATE or REPLACE I still get the error (P.S. I looked at the code and it uses TABLEUPDATE(,T.,.T.) in the method used by the save button).

I wasn't talking about the user functions. It looks like the code behind the scenes does an APPEND when the user chooses to edit the record. Or, the code does something like GATHER and is on the wrong record. What do GETFLDSTATE() and RECNO() report on the TABLEUPDATE() line. Changing field B when field A is candidate key does not trigger the error message you are seeing.