Intelligent Waiter Schedule

I would like to set waiters within a specific range, not just specific times. I want to have the ability to book, say, 2 waiters within a range (e.g. 9AM-to-10AM) but my Appt Schedule is setup every 15 minutes. Would like the ability to book 2 waiters within the hour and the waiter slots available adjust depending on the the range, instead of the individual slots.

Example: We set that we can only book two waiters from 9am-10am. The shop is set-up with 15 minute intervals. If I book a waiter appointment for 9am, I want DealerMine to have the logic to know that there is still one Waiter slot open for the Appointment Coordinator to book out of the remaining time slots in the hour (9.15,9.30 or 9.45).