Hide/unhide scroll bar

I want to be able to hide the scroll bar when its not needed.. this is the AS on the button:

on(release){
_parent.newsBox.text = _parent.newsBox.text;
_parent.scroll2._visible = (_parent.newsBox.maxscroll > 1);
}


and this is the action on the frame:

scroll2._visible = (newsBox.maxscroll > 1);
newsBox.onChanged = function() {
scroll2._visible = (this.maxscroll > 1);
};


I took this from a tutorial so I am sure I have this wrong..

Can anyone help?

thanks