Message error

I suggest you make use of triggers to take control over the default message.

You can try triggers such as ON-CLEAR-DETAILS trigger.

I would write ON_MESSAGE trigger on block level, trap particular message with built ins MESSAGE_CODE, MESSAGE_TEXT and handle the error...

If it an oracle error you are trying to trap than I would use ON-ERROR trigger on specific block, use built ins DBMS_ERROR_CODE, DBMS_ERROR_TEXT to trap the error.