I’m adding LED back-up lights that I want to control with a switch, but also activate from the factory back-ups. I plan to use a relay, but can I trigger from the switch AND the back-up light circuit? If so, will one (or both) factory back-up lamps be powered when I turn on the switch, i.e. since the trigger wire from the switch and the back-up circuit will be combined, will the switch back feed the factory lamp(s)? Thanks in advance for your help!