A computed-for-display field whose formula replaces the default error message with a customized message.
For example, this formula for a field named CustomString on a $$ReturnAuthenticationFailure form gives more information to the user if authentication fails. The formula takes the value from the default MessageString field if it contains "unauthenticated" and replaces it with instructions to the user. If the MessageString field does not contain the word "unauthenticated", Domino uses the value of MessageString instead.
@If(@Contains(messagestring;"unauthenticated");"Sorry, the name and password you entered are unknown in our system. If you are new to our site, return to the home page and follow instructions for registering.";messagestring)