Create a Global Boolean: TimerActive = True
Add the Event is TimerActive = True as part of the Every 0.001seconds event
(this should have no effect of the game)
Whenever the player finish the game then set an action: TimerActive = False
This will stop your timer from ticking.
You can then do what you need with the numbers you have stored in MSPassed, SecPassed, and MinutesPassed