Shifting Light Wall

I am furthering my experiments using Grasshopper as a parametric tool for lighting design. In this instance, I am designing a light feature wall for my spa. The idea is that wall has two sets of lights: gentle pink cans in the background, and purple lights in front whose size and intensity is controlled by an aperture. As a person walks across the floor, pressure sensors detect the position and calculate a point in room. The distance of each light from the new point is determined and the apertures of the purple lights are adjusted. So, as the person crosses the room, the should be constant shifting of the lights.