GUICtrlSetOnEvent need help

[mrmimi]

#include <GUIConstants.au3>

Opt("GUIOnEventMode",4)

GuiCreate("alogin", 482, 300)

GUISetOnEvent($GUI_EVENT_CLOSE, "stop")

;------BUTTONS------------------------------------

$stop = GUICtrlCreateButton("Exit", 110, 160, 70, 25)

GUICtrlSetOnEvent($stop, "stop")

$Start = GUICtrlCreateButton("Start", 10, 160, 40, 25)

GUICtrlSetOnEvent($Start, "GO")

;-------------------------------------

GUISetState()

While GuiGetMsg() <> $stop

WEnd

;---------FUNCTIONS------------------------

Func stop()

ToolTip("i wanna quit ...",470,395)

Sleep(500)

exit

EndFunc

func GO()

ToolTip("A long cycle ... Stop me pls------------------",500,300)

;-------------long cycle here.....like Sleep(9999999999) - so i need to stop it with "Exit" Button?but how ?

Sleep(100000000)

EndFunc

[xcal]

Hmm this looks a lot like this.