Help with global preloader

Hi to everybody:
I need your help, because at the last days I was searching in diferents forums and pages for a solution to my problem with preloader.
I have a main movie that it,s and interface with the buttons, and I want to load externals swf when I press the buttons inside and empty mc called “cargador”.
It works ok.
My problem it,s that I want to put a preloader in the main movie for all the external movies, with a bar and text progress, that appear when click and dissapear when the external movie was loaded.
I thing that it works with a funcion, or maybe put the preloader in a diferent movie and in a level, but I,m new in actionscript and after a lot of days, I can,t do it.
Somebody can explain how to do it?
Thanks to everybody.
Sorry for my english
Greetings from Spain