How do I set Appointments+ to only take bookings that are made 72 hour in advance?

Hello!

What I'm looking to do is set Appointments+ to only accept bookings if they are made 72 hours in advance of the time of booking.

Because some treatments on offer need a 48 hour allergy test, this is something we need to build into the booking process.

Your help is much appreciated!

Thank you...

Chris