Perspective move

1

I am trying to create a bowling ball type effect where you can place a ball anywhere on the x axis you want and then watch it roll towards a vanishing point. I’ve tried the tutorials on this page and am using the code below but I don’t have any control of where the ball starts, what size it will be etc. How do I make it so that I can place the ball where I want visually and then let it roll?

 onClipEvent (load)
{
   z=700;
   zspeed=200;
   fl=300;
   xcenter=_root.vanishPoint._x;
   ycenter=_root.vanishPoint._y;
   offx=_x;
   offy=_y;
}
onClipEvent(enterFrame){

   scale=fl/(fl+z);
   _x=xcenter+offx*scale;
   _root.ballx=_x;
   _root.bally=_y;
   _y=ycenter+offy*scale;
   _xscale=_yscale=100*scale;
   z+=zspeed;

}