Error message if "Type" is not selected

It would be nice to have an error message pop up (sort of like the "cannot be save" message) if they "Type" field is not selected. 

Ex...if a technician marks a ticket completed and the type field is not changed from "must change" or "update this", when they try to save it, it will throw up an error message telling them that the "Type" field must be changed prior to marking the ticket completed.