Fade out function

[fabrizzzio]

Hi there guys,
I have this code in flash (AS2)... check it out:

interior._visible = false;
back._visible = false;

function fadeout() {
onEnterFrame = function () {
this._alpha -= 10;
if (this._alpha <= 0) {
this._alpha = 0;
delete onEnterFrame;
}
}
}

gointerior.onRelease = function() {
interior._visible = true;
interior.gotoAndPlay(2);
fadeout();
};

stop();

I have a couple of movie clips in the layout, and a button called "gointerior"
The idea is that when I release that button, it fades out (the button). So I have created a function called fadeout(); but when I call that function and I test the movie all the movie fades out. I dont know what Im doing wrong. I think that is something related to the function path or something.
I need your help guys!