Sprite Movement [RPG Style]

programming flash
1

Well guys, i have a problem when moving sprites. I manage to make the sprites move and get back to their position after i release the key. But when i stay with the key pressed, the image of the sprites moves, but the animation doesn’t seem like it’s walking. It’s stays frozen.

This is my code:

All the “hero#” are MC

onClipEvent(load)
{
 step=5;
 movieWidth=300;
 movieHeight=300;
 movieheight1=0;
 this.stop();
}
 
onClipEvent(enterFrame)
{
 if (Key.isDown (Key.RIGHT) && this._x < movieWidth)
  {
  this.attachMovie("hero1", "hero2", 10);
  this._x+=step;
 }
 if (Key.isDown (Key.LEFT) && this._x > 0)
 {
  this.attachMovie("hero3", "hero4", 10 );
  this._x+=-step;
 }
 if (Key.isDown (Key.DOWN) && this._y < movieHeight)
 {
 this.attachMovie("hero5", "hero6", 10 );
 this._y+=step;
 
 }
 if (Key.isDown (Key.UP) && this._y > 0)
 {
 this.attachMovie("hero7", "hero7", 10 );
 this._y+=-step;
}
}

This is the SWF so you can judge it by yourself:
http://www.petaimg.com/u211/187123qw.swf