Stopping a movie generating shapes

Question

Hi.  I'm hoping someone can help me stop this.  Any help getting this thing woring would be much appreciated.  The code comes from this site:
http://www.pixelhivedesign.com/tutorials/Realistic+Flash+Smoke+Effect/
He creates a movieclip called aPuff and then gives the movieclip an identifier of aPuff as well.  It generates a smoke-like effect which is really nice; however, I'm wanting to get it to stop at some point...preferrably by allowing the last puff to go up and fade out.
How can I accomplish that?
Thanks again.
// Realistic Smoke Effect - www.pixelhivedesign.com
fadeSpeed = 1;    // Smoke fade speed.
floatUpSpeed = 2; // Smoke float up speed.
// Every frame attach a puff of smoke.
this.onEnterFrame = function(){
  // Get next available depth.
  d = this.getNextHighestDepth();
  // Attach a puff of smoke.
  aPuff = attachMovie('aPuff','aPuff'+d,d);
  // Set initial scale to 10%.
  aPuff._xscale = aPuff._yscale = 10;
  // Put puff where the mouse is. (add small random)
  aPuff._x = Math.random() * 5;
  // Randomizes the starting animation for realism.
  aPuff.gotoAndPlay(Math.round(Math.random()*20));
  // Smoke will animate each frame.
  aPuff.onEnterFrame = function(){
    // Scale smoke up.
    this._xscale = this._yscale += fadeSpeed;
    // Fade smoke.
    this._alpha -= fadeSpeed;
    // Smoke floating up.
    this._y  -= floatUpSpeed;
    // When smoke is 100% scale, remove it.
    if(this._xscale >= 100){
      this.removeMovieClip();

Answer 1

use
delete this.onEnterFrame
when you want to stop creating new puffs.