Maybe this can help... Simple approach... 
  
#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>
 
 
Global $onoff1 = 1
 
GUICreate("MY GUI")
 
$button1 = GUICtrlCreateButton("OFF", 50, 50, 50, 50)
$button2 = GUICtrlCreateButton("OFF", 150, 150, 50, 50)
$button3 = GUICtrlCreateButton("OFF", 250, 250, 50, 50)
 
GUISetState()
 
While 1
 
$msg = GUIGetMsg()
 
If $msg = -3 Then Exit
 
If $msg = $button1 Then
If $onoff1 = 1 Then
GUICtrlSetData($button1, "ON")
$onoff1 = 0
Else
GUICtrlSetData($button1, "OFF")
$onoff1 = 1
EndIf
EndIf
 
;continuwe here
 
WEnd