Click to load, click again to unload

programming flash
1

i have a button that loads a movie clip when clicked, how do i use the same button to make the movie disappear when i click on the button again?

my current code…

for the button

on (release) {
window.loadmovie(“slideshow.swf”);
_root.Y = 1;
}

the movie clip where the movie load into

onClipEvent (enterFrame) {
if (_root.Y == 1) {
this._alpha = 100;
} else {
this._alpha = 0;
}
}