Loader component problem

Hi
I am working on a flash website whose size may reach a total of 7 MB. That’s why I have split the main content of the site into separate, smaller movies which are externally loaded into the main movie using loader and a progress bar. There’s a numeric ticker in a movie clip in that movie which when clicked, is supposed to change the text size of a text box. It targets the dynamic text box from _root. Here’s the code:

form.change = function(eventObj){
txtchange=new TextFormat();
txtchange.size=base.txtsize.value;
_root.mainContent.setTextFormat(txtchange);
_root.scrollbar.setScrollTarget(_root.mainContent);
if(txtsize.value<=12){
_root.scrollbar._alpha=0;
}
if(txtsize.value>12){
_root.scrollbar._alpha=100;
}
_root.scrollbar.visible=true;
_root.scrollbar._alpha=100;
}
base.txtsize.addEventListener(“change”, form);

Here, txtsize is the numeric ticker, base is a window which is a movie clip in which txtsize is, and mainContent is the text in _root that is being changed. It works perfectly when I run the external swf on its own, but when I open it from my main movie with the loader, nothing happens!

I played around with this with another external movie to fix this bug, and found that when I use _root from the loaded swf, it targets the parent swf. Please help me!