Just a little correction: Query() has been replaced with QueryGadget() since Version 1.4, so the correct code since then is:
Extern "win32" Function GetWindowLong(hwnd, nIndex) = "GetWindowLongA@8" Function SetWindowLong(hwnd, index, nIndex) = "SetWindowLongA@12" End Extern Local Window:TGadget = CreateWindow("Testing", 10, 10, 512, 512, 0, WINDOW_TITLEBAR) hWnd = QueryGadget(Window, 1) ret = GetWindowLong(hWnd, -16) ret = ret | $20000 SetWindowLong hWnd, -16, ret UpdateWindowMenu Window Repeat WaitEvent() Until EventID() = EVENT_WINDOWCLOSE