onEnterFrame question ppl :)

[color=black]ok i have some what of a problem

iam loading in jpg’s thru xml – now when they load in they are fading in
so i have this
holder_mc is my movieClip they are loaded into

this.onEnterFrame = function(){
holder_mc.onEnterFrame = function(){
holder_mc._alpha +=20;
}
}

its probly wrong or so but

how would i delete the on enter frame* [color=Red]for both[/color]* and start the fade again when i press the button to load another picture
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