Need To Create A Preloader For A Movieclip

Relatively new to AS 3.0. Here is what i want to do and am struggling-

have a bunch of thumbnails which when clicked will load Movieclips (slideshows) on the fly. These movieclips have been exported for AS. I have an empty movieclip on the main timeline into which i am loading these slideshow movieclips.

How do i create a preloader before each of these movieclips that are being loaded, so that it runs the preloader first and then loads the slideshow. im doing this as i have many thumbnails.

code im using for slideshow instance-

var s1:slide1= new slide1();

putting the abv into the empty movieclip (hol) on the stage-

*hol.addChild(s1);
*
This works fine for all the thumbnails and the overall page/swf is working perfect. Only thing lacking is a preloader before each slideshow.

Pls pls adviseā€¦

best regds