The light will need constant 120vac, neutral, and ground...it depends on how the switch is wired and what passes through the box there. Now, if you want the added flood to be controlled via that switch as well, it may work, depending on the one you choose. I have one hooked up in my stairwell to a 3-way switch. If you flick the switch, it turns the light on and it overrides the motion sensor. If you just turn it on once, it relies on the motion sensor to turn the light on and off. I also has a photocell, and won't automatically turn on in the daylight unless you do the override trick.