I would think the target would need "painted" for a certain amount of time to count? Then you want to identify who hit it?

Have each laser pulse at a different rate. 75hz, 100hz 125hz... Doable with cheap lasers.
Then have the target PIC COUNT the incoming pulses for a second. If the COUNT variable = 100 then whatever.

I use a similar method for a "laser fence". If the target does not see Xhz then the alarms sound. A photo-transistor sits in the bottom of a reflective funnel about 2 inches in diameter at the opening for the target.