Stop Activity Process by changing an Appointment Result

I currently have automated emails set up for customers that are on the fence in moving forward.  (5, 10 and 30 day emails, when the appointment result is "Presentation/Maybe").  If the customer calls us on Day 7 and says that they went with someone else or they would like to go forward with us, the emails continue unless we manually stop them.  I would like the emails to auto stop if the appointment result is change to "Presentation / Won" or "Presentation / Lost".