

In the dialog "Edit Event" there is a check box "Lock Front Panel ..." this box should be unchecked for the stop buttons to work.
Your current implementation is difficult to understand.
1. Try to fit your code into a maximum screen size of 1024x768.
2. Try to avoid using while loops in while loops (less scalability, projects tend to grow larger).
3. Build a state-machine : init state(set all intial variable states), main state (handle all user interaction with the event structure), quit state (reset all variables and exit application nicely).
4. Migth not be important now, but try to keep execution time in event case short (not important when user cannot interact during chosen function)
Hope it helps, if not someone else probably adds to my comment.
Regards,
André (CLA, CLED)