I agree with this advice. I use to work for Honeywell and we often use to use relays to separate the programmable thermostats from the furnace control so I have some experience in this. If you need any help wiring it PM me and I'll draw up a schematic for you. I suspect, since you knew to ask about using a relay, you already have this covered.How many amps is your microswitch rated for? It will say on the side of it. 2 X100 watt bulbs draws about 1.67 amps at 110 volts. If your switch is rated lower than 1.67 amps at 110 volts, you will need a relay, but I would say if its rated for less than 2 amps you should add the relay. If you are pushing the switch near its maximum capacity, it will shorten its life. If the switch is rated for more than 2 amps at 110v there is no advantage to adding a relay.