Gravity problem

1

Hello,

I am building a platform game.
There is a problem. I have two MovieClip, one of the player, and one of the enemy. On both of them works gravity. I use attachMovie to attach them to the stage.
my code is:

var grav:Number = 0;
var gravity:Number = 2;

enemySpawn = function(numEnemies){
	for(i=1;i<=numEnemies;i++){
		attachMovie("enemy", "enemy"+i, i);
		enemy2._x = 200;
		_root["enemy"+i].onEnterFrame = function(){
			this._y += grav;
			grav += gravity;
			while(ground.hitTest(this._x,this._y,true)){
				this._y -= gravity;
				grav = 0;
			}
		}
	}
}
enemySpawn(2);

Fla file is attached.

Thank you to the all those who helpful!!!