Notifying trainers when people sign up for their class

I'm developing a website for a gym where customers can sign up for individual classes, or buy year-long passes to classes. I am treating these year-long passes as service products. Is there a way to automatically notify individual instructors (via email) when someone signs up for their class? 

For example, if I sign up for Jim's strength training class, Jim will receive an email informing him of my signup.

Is this possible? The closest thing I can find so far are the custom forms you can add to checkout, but there's no way to edit the storage destination.