trying to use light.

I encountered some problems when I experimented with lighting. For starters, its much more difficult to get the perfect lighting than it seemed in the tutorial or as it would have originally seemed. But the main problem was that I wanted to start with a target spot light and gradually turn it into an omni light and then back to target spot in my animation. However, I seem to be unable to control different lights in different stages of the animation. I can only (at the moment anyway) put one light on for the entire animation.