| | Re: Should I be worried or is it a joke?
If he had an affair and you both rug swept it then its apparent from the messages he hasn't really changed his behaviors to not put himself in the line of fire - in fact he is inviting it and testing his married coworker who seems to be not embracing the comments due to probably respecting his own marital boundaries. So yes you should be concerned about this. Maybe your H is planning a fling or not, but he is certainly trying to be open to it.
So make your boundaries on this clear - this business trip is no excuse for innappropriate behavior, if your H wants your trust he will change his tune, apologize and discuss this, and make every effort to keep you informed the whole trip of what he is doing.