With ProcessMessages you could make a procedure like follows that would run if the hotkey was pressed, and you run the ProcessMessages command.

CODE
//Put ProcessMessages in your code whenever/wherever you want to check for HotKey
ProcessMessages

Procedure Hotkey1 When {GlobalKeys} contains $Hotkey
While 1 = 1
TimeStamp Hotkey pressed

If {GlobalKeys} contains $StopKey
Exit
Else
Delay 50 //Always include a delay when running infinite loops
End
End
ClearGlobalKeys //Keep procedure from running repetitively when the hotkey isn't pressed
End


Call is pretty much the same idea if you've only got one procedure to run. ProcessMessages allows you to go through any procedure with When, On, and Every keywords. These are all listed in the help under Procedure and ProcessMessages.