But the try-catch approach is probably the better one. Something like this:

BEGIN TRY

INSERT INTO tblCustomer (cid, lName, fName)

SELECT @cid, @lName, @fName

END TRY

BEGIN CATCH

IF error_number() = 2627 UPDATE tblCustomer SET lName=@lName, fName=@fName WHERE cid=@cid

END CATCH

It seems to work...