Just want to add what Grigore told.
The answer depends on how you want to control it. ON KEY works for manual control. I would use uncommon button combination to do it, like {ALT+2} instead of buttons like F10 having other functionality in Windows. Instead of 'QUIT' you can use EXIT, CANCEL or other commands depending on what you need.
If you want to control the loop in the code, you may set some options like looptime or number of loops and EXIT loop on that condition.

Hope this help