Best way for preloading

Whats the best way to preload content if its dynamic?

Structure as follows:
Main swf (which contains all the variables etc and loads Navingation swf)
Navigation swf (which loads page1, page2, page3, page4)
Page1-4 swf (which all load content dynamically also)

When loading navigation swf in to main swf, will that also load page 1-4? or how do i use actionscript just to load files as i need them.

If anyone needs any clearer info about how i have structured things just ask!

Cheers! :sen: