Sounds very achiveable but exact ins and outs will depend on how your setting them at the minute.
Can you show how you have your type tag setup and made mandatory?
I have 2 Ticket Tags by the name TICKET TYPE & WAITER
TICKET TYPE (Dine In, Car Order, Take Away)
WAITER (Waiter1, Waiter2…)
If the user selects Dine In or Car Order from TICKET TYPE then either system should prompt for selecting the WAITER or should not allow to close ticket without adding a TAG for Waiter