>When I seup database triggers for a table the default 'Trigger Failed' message is fired if the Trigger fails. How can I replace this message with my own message. If I call a function from the trigger to display the message, the default message still fires after my message.

You could trap error in code:
Local lErrorflag
ON ERROR lErrorflag=.t.
INSERT into .... && any command may cause trigger failed
ON ERROR
IF lErrorflag=.t.
**** error handling code
=messagebox(.....)
ENDIF