Flash MX Preloader

Hi, i have a .swf file (interface.swf) that acts as the _mc which will retrieve several external .swf files and display them in it. I would like to add a preloader (using the flash mx 2004 progress bar) to show the loading process (interface.swf will load the first external .swf once it has downloaded part of the .swf ---- not load after all the external .swf files have been loaded totally) therefore i would like this preloader to only detect the process of downloading the first external .swf… Is there anyway i could do this?

Thanks.