I was afraid of some kind of technical restriction that would get in the way. What would be a simple, $300-to-code alternative way to schedule the phone's ring

I was afraid of some kind of technical restriction that would get in the way. What would be a simple, $300-to-code alternative way to schedule the phone's ringer, preferably based on existing calendar appointments? Otherwise I'd have to nix that platform & lessen the price of the job by $300.