This is what i am tryng to do:

I have a customer that has a sports court. He wants me to create a button on an RK- that turns on/off the lights at the sports court. What i did was i found a 12v coil contactor and attached it to one of the relay outputs on the XP8. Press the button on the RK3 and the lights turn on/off.

Now the customer wants to have a push button or switch outside to also control the lights. My thought was to have a doorbell button powered by a 12v power supply and have the output of the button go into a sense input on the XP8. I am sure that will work. But from here i am lost. I do not understand how the RK3 will know if the lights are on or off from the button. Figured out that i will need to use some flags but not sure how to program it. Anyone have any suggestions?