You can get a handle to the event and then enable, disable, or toggle its state:
Code:
enterEvent = manager.onEnter(sensor, EnterProximity)
exitEvent = manager.onExit(sensor, ExitProximity)
vizact.onkeydown('1',enterEvent.setEnabled,viz.TOGGLE)
vizact.onkeydown('2',exitEvent.setEnabled,viz.TOGGLE)