Animating filter effects, how would I slow the speed?

Hello, I’m learning about animating filter effects from the tutorial here:
http://www.kirupa.com/developer/flash8/filter_effects.htm

My question is, how would I change the speed of the effect and slow it down.
The problem is I’m only changing the strength of glowfilter from 0 to 2 on a mouseover, and since the code adds one 1 to it every frame, its a little choppy.
Here’s my code:

    import flash.filters.GlowFilter;
    var gf:GlowFilter = new GlowFilter(0xFFFFFF, 100, 3, 3, 0, 3, false, false);
    bar_mc.stackedWord.filters = [gf];
    bar_mc.stackedWord.onRollOver = function() {

    this.onEnterFrame = function() {

    if (gf.strength < 2) {

    gf.strength++;
    } else {

    delete this.onEnterFrame;

    }
    this.filters = [gf];

    };

    };
    bar_mc.stackedWord.onRollOut = function() {

    this.onEnterFrame = function() {

    this.filters = [gf];
    if (gf.strength > 0) {

    gf.strength--;

    } else {

    delete this.onEnterFrame;

    }

    };

    };

Any help would be appreciated!
Thanks