My horse barn is 400' away from my house and I would like to be able to turn on a light at the barn from my house.Can I run 12/3 this far and if not ,what would be another way to do this? The lights would be two 100watt or less.

The distance is the issue, but yes you can do it for the lights.

NEC says 5% max voltage drop. At 200 watts, you are just under 5%.