Controlling servo with PIR sensor

I am not sure how I should approach this, but what I am trying to do is have 3 PIR senors place on the left, middle, and right side of a board so they would detect body heat, and the servo will turn toward which ever sensor picks up the most heat.

thanks in advance!

There is a thread here;start=all that discussed some way to use sound sensors to cause a robot to turn toward the direction of sound. Although you will be using different sensors, the concepts may be close to what you need for your app. The design evolved as the thread progressed so you may want to read all the way through before deciding if its applicable to what you want.