Relative URL(?) for load movie into movie in movie

I need help to understand how to make a movie loaded into another movie understand it´s relative position in the folder system on my server.
A.swf is located i folder MAIN. B.swf located in folder B in folder MAIN loads into A.swf. Then I need to load 01.jpg located in folder PICT in folder B into B.swf without doing; URL: B/PICT/01.jpg but rather URL: PICT/01.jpg since B.swf is already in folder B.
As you understand I´m not the script guru. Grateful for hints on where to look to learn more about this!