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;-------------------------------------------------------------------------------------
; Function: Subclass
;         Helper function to subclass control
;
; Parameters:
;         hCtrl   - handle to control
;         func   - window procedure
;         cbOpt   - callback options, by default ""
;
Subclass(hCtrl, func, cbOpt="") {
   oldProc := DllCall("GetWindowLong", "uint", hCtrl, "uint", -4)
   ifEqual, oldProc, 0, return 0
      
   WndProc := RegisterCallback(func, cbOpt, 4, oldProc)
   ifEqual, WndProc, , return 0
      
    return DllCall("SetWindowLong", "UInt", hCtrl, "Int", -4, "Int", WndProc, "UInt")
}

if !SubClass(hwndList, "MyWindowProc")
     MsgBox, Subclassing failed.
...
MyWindowProc(hwnd, uMsg, wParam, lParam){

    if (uMsg = .....)  ; my message handling here

   return DllCall("CallWindowProcA", "UInt", A_EventInfo, "UInt", hwnd, "UInt", uMsg, "UInt", wParam, "UInt", lParam)
}