How do I watch Acuity for upcoming appts

I’m trying to create a scenario that looks at upcoming Acuity Scheduling appointments and then send an SMS through Clicksend an hour before start time.

This operation is simple in Zapier because it has a hook/event called Appointment Start. But for the life of me I can’t figure out how to perform the same task in Make.

It’s important that my scenario only pick up appointments within, say, 8-12 hours of start time. It cannot pick up appointments when they’re initially scheduled because I don’t want to send out text reminders if the appointment was cancelled or rescheduled after it was booked.