I would give this a shot.
revoke authority to their message q such that they only had read, and add authority. i think that will allow them to see what's in the q and add new messages but not be able to change or delete messages. be sure that any admin id's have all authority to the q.
have not tried this.
HTH
Mike Butler
Iseries Guy -> PC's gone, SUNs gone - WooHoo
"Never put off 'til tomorrow what you should have done yesterday