Random generator interaction question

I have the following code for a movie clip to generate random squares and move them around.

onClipEvent (load) {
//data you may want to change
width = 600;
height = 400;
speed = Math.round(Math.random()*2)+1;
//initial positions
x = this._x=Math.random()*width;
y = this._y=Math.random()*height;
x_new = Math.random()*width;
y_new = Math.random()height;
}
onClipEvent (enterFrame) {
//x movement
if (x_new>this._x) {
sign_x = 1;
} else {
sign_x = -1;
}
dx = Math.abs(x_new-this._x);
if ((dx>speed) || (dx<-speed)) {
this._x += sign_x
speed;
} else {
x_new = Math.random()width;
}
//y movement
if (y_new>this._y) {
sign_y = 1;
} else {
sign_y = -1;
}
dy = Math.abs(y_new-this._y);
if ((dy>speed) || (dy<-speed)) {
this._y += sign_y
speed;
} else {
y_new = Math.random()*height;
}
}

this code is on a square which was converted to a movie clip
the timeline frame has this code:

i = 0;
while (i<25) {
//duplicateMovieClip(dot, “dot”+i, i);
dot.duplicateMovieClip(“dot”+i, i);
i++;
}

I would like all the squares to stop moving and fall off the bottom of the window when the user clicks anywhere in the feild. ideas?