Omnisec

I have been looking around the forums and internet for a scoring system for arma 2 OA, I am making a training mission and would like to score +1 point if a person hits a small targed (RED) and -1 point if the person hits a big target (Black), its as simple as that. So something like a hint where it tells the score when a target is hit and keeps adding the score or taking away the score dependant on the target hit. I would appreciate any help with this, thanks.