UNLOAD swf file from nav button

I can load swf file from nav buttons. Gallery page is my default page. When I click about button **I want gallery.swf to unload and about page to show up.
**
Currently, gallery page is still in the background when I click about page.
Gallery page is removed if I click about page again. How do I fix this?

var pageLoader:Loader = new Loader();

galleryBtn.addEventListener(MouseEvent.CLICK, galleryPage);

function galleryPage(e:MouseEvent):void {
var page:URLRequest = new URLRequest(“nature.swf”);
pageLoader.addEventListener(MouseEvent.CLICK, unloadPage);
pageLoader.load(page);
addChild(pageLoader);
};

aboutBtn.addEventListener(MouseEvent.CLICK, aboutPage);

function aboutPage(e:MouseEvent):void {
var page:URLRequest = new URLRequest(“about.swf”);
pageLoader.addEventListener(MouseEvent.CLICK, unloadPage);
pageLoader.load(page);
addChild(pageLoader);
};

function unloadPage(e:Event):void {
var pageLoader:Loader = e.currentTarget as Loader;
pageLoader.unload();
removeChild(pageLoader);
}