Help with Flash player's security sandbox

I’m writing a flash application for PDAs right now, and I’m having an issue. I’m hoping it has something to do with flash player’s sandbox security model and not with the fact that flashplayer 6 for ppc is weird.

So, here’s my situation. I have a main swf file and “section” swfs. The main swf file loads the section swfs in a cointainer movie clip with the loadMovie method. There is some interaction between the clips. The main swf calls functions on the section swfs, and the section swfs need to call functions on the main swf.

Here’s where things get messy. The main swf file has to be on the PDA, the section swfs are on the server, and I launch the main swf on its own, because it has to be fullscreen and a browser won’t let me do that. The problem is that the section swfs can’t make callbacks to the main swf. How can I fix this? I know I probably need to put a crossdomain.xml file somewhere, but I’m not sure. Is there something I can write on the actionscript itself to allow callbacks?