Loading swf files into different levels

Hi folks, I followed this tutorial which was very usefull:-

http://www.kirupa.com/developer/mx/preloader_transition.htm

Now I’ve got my main buttons level which has 9 buttons. A few of
these buttons load a second level of choices. These choices inturn will call a third level of thumbnails that will display images.

What I want to do is have each choice level loaded as a external swf then inturn they call the thumbnails data file which is a swf file.

My problem is that after loading the mainlevel I can get the second choice to load into the blank “mc”, but I just can’t get that choice level to load the third level external swf file.

I need serious help to sort this ASAP.