Maybe something like this :
#include <MsgBoxConstants.au3>
HotKeySet("{ESC}", "_Terminate")
HotKeySet("{F8}", "_PauseScript")
Global $bPaused = False
; Main Loop
While 1
Sleep(100)
WEnd
Func _PauseScript()
$bPaused = True
ToolTip("Script is paused", 10, 10)
If MsgBox(0, 'Pause', 'Script is paused') = $IDOK Then
$bPaused = False
ToolTip("")
Return
EndIf
EndFunc ;==>_PauseScript
Func _Terminate()
Exit
EndFunc