onClipEvent(enterFrame){
  if(player_1.hitTest(_root.player_2._x, _root.player_2._y, true)){
    "Code to execute on hit here";
  }
}

MovieClip.prototype.life = 100;
MovieClip.prototype.maxLife = 100;
//all the attacks from the characters will be acummulated here
MovieClip.prototype.atks = new Array();
//
player1 = new MovieClip();
/*
the attacks will be writen this way:
[ minum damage, difference beetwen max damage and minimun damage, accuracy]
*/
player1.atks.push([5, 5, 100]);
player2 = new MovieClip();
/*
//this code modifies the life of any of the two characters
//(if their life is negative, it is automatically turned into 0;
//if it's more than it's max life, its turn into the max life)

//note: you need the movieclip to have a maxLife variable.
*/
MovieClip.prototype.setLife = function(amount) {
   this.life += amount;
   if (this.life<0) {
      this.life = 0;
   }
   if (this.life>this.maxLife) {
      this.life = this.maxLife;
   }
};
/*
//This code is for the attack itself. To make it work, you should introduce which attackç
//the char is using, and to which target
*/
MovieClip.prototype.attack = function($attack, target) {
   //this gives you the possibility of missing
   if ($attack[2]>(Math.random()*100)) {
      //NOTE:
      //Create an integre random number of the difference...
      // in other words, if 10 is the minum, and 15 is the max
      // then the extra will be a random number beetwen 0 and 5,
      //and it will be added to the min damage
      var minDamage = $attack[0];
      var extra = Math.round($attack[1]*Math.random());
      var modification = (minDamage+extra)*-1;
      target.setLife(modification);
   }
   else {
      trace("attack missed");
   }
};

player1.atks.push ([10,5,100])
player1.attack(player1.atks[1],player2)