Child > Parent >child preloading as3

I have been using:

yourbutton.addEventListener(MouseEvent.CLICK,f);

function f(e:Event):void{

Loader(this.parent).load(new URLRequest("newswf.swf"));

}

which was suggested to me in a different post to target the parent loader class, however i now no longer can reference my preloader in the parent swf

(extract from the parent swf):

var my_pb:ProgressBar = new ProgressBar();

my_pb.source = my_loader.contentLoaderInfo;

my_pb.x = 305;

my_pb.y = 293;

my_loader.load(new URLRequest("contentLoader.swf"));

this.mainTemplate.mcMaskedClip.addChild(my_pb);

my_loader.contentLoaderInfo.addEventListener(Event.COMPLETE, finishLoading);

function finishLoading(e:Event):void{

this.mainTemplate.mcMaskedClip.addChild(my_loader);

this.mainTemplate.mcMaskedClip.removeChild(my_pb);

}

How do i target  the parent loader class to use the preloader?

the reason i need a pre loader are the swf files i am loading are fairly big i.e. 2-5mb

keith