setInterval + duplicateMovieClip -- please Help!

1

I’m trying to modify this script so that instead of using the onPress to trigger the duplicateMovieClip I can use the setInterval, here’s my script:

_global.globali=0;
particle = function () {
    // PURPOSE: defines the particle object
    // 
    // initialize properties
    this.speedX = (Math.random()*8)-4;
    this.speedY = (Math.random()*8)-4;
    this.lowX = 0;
    this.lowY = 0;
    this.highX = 550;
    this.highY = 400;
    
    // END initialize properties
    // 
    // Define events
    this.onEnterFrame = function() {
        if (this._x<this.lowX) {
            this.speedX = Math.random()*4;
        } else if (this._x>this.highX) {
            this.speedX = -Math.random()*4;
        }
        if (this._y<this.lowY) {
            this.speedY = Math.random()*4;
        } else if (this._y>this.highY) {
            this.speedY = -Math.random()*4;
        }
        this._x += this.speedX;
        this._y += this.speedY;
    };
    setInterval( function(){
        trace("interval called"); 
        this.duplicateMovieClip("clip"+globali,globali);
        particle.apply(_root["clip"+globali]);
        _root["clip"+i]._alpha=random(100);
        globali++;
        }, 5000 );
    
    this.onPress = function() {
        this.duplicateMovieClip("clip"+globali,globali);
        particle.apply(_root["clip"+globali]);
        globali++;
        
    };
    // END define events
};
//
// main code
particle.prototype = new MovieClip();
for (i=0; i<1; i++) {
    _root.attachMovie("ball", "ball"+i, 1000+i);
    particle.apply(_root["ball"+i]);
    _root["ball"+i]._alpha=random(100);
}
// END main code

It seems to work in the trace, but the actual movieclips aren’t appearing.

Here’s the original FLA as well for reference: www.globaleyes.ca/particles.fla

Thanks for any help!