im not a good scripter but aint (curent position - shedposition = distance to get back)

then use x,y,z translate to get back to it with the distance you get from the calcul from abouve then if distance <= 0 , somehting else happen liek going back to another tree

Might want to include a check everytime you add a a hit. Something like this(provided I dont know how you've done your code)

function HitTree(){
hitCount+=1;
if(hitCount == 5){
    hitCount = 0;
}

}

is that what your looking for?