Thanks for your reply. I made the changes as suggested and also change the criteria. It works but tblCust.Custid and tblCust.CState enter parameter popup asking for the user for input. I don't want the user to be confused by this each time they run the query. How do I get rid of this and still make this query work please?
Code:
INSERT INTO tblCust ( Custid, CState )
SELECT tblstcu.cust, tblstcu.nstate
FROM tblstcu
WHERE (((tblstcu.cust) Not In ([tblCust].[Custid])) AND ((tblstcu.nstate) Not In ([tblCust].[CState])));