Buttons and movie clips problem..Help!

I´m newbie here, so any help would be appreciated. My problem is that I don´t know which action to use to get my buttons and movie clips to work.
I have five buttons and five movie clips, so when I click on a button it calls a specific movie clip, but when I click on the next button, next movie clip appears, but the previous movie clip stays on the scene…How can I make it disappear?

here is a buttons code

on (rollOver) {
this._alpha=100;

}

on (rollOut) {
this._alpha=100;

}

on (release) {
tellTarget ("_root.bart1") {
gotoAndPlay(2);
_x=200;
_y=220;
}
}

onClipEvent (mouseMove) {

dist=Math.sqrt(Math.pow(Math.abs(_xmouse),2)+Math.pow(Math.abs(_ymouse), 2));

if (dist<=_root.menutriggerdist) {
currscale=(1-(dist/(_root.menumultiplier*_root.menutriggerdist)))*(_root.menumaxscale-100);
this._xscale = currscale;
this._yscale = currscale;

} else {
this._xscale = 100;
this._yscale = 100;
}
}

…and here is a movie clips code

onClipEvent (load) {
_xscale = 100;
_yscale = 100;
}

In the first frame of the movie clips i´ve put stop(); action, and in the second frame play();