Access instances for custom class

Hey guys,

say I have a shell that loads main.swf, the shell has a document class of Shell.as and the main.swf has a document class of TemplateBase.as now I need to write another class to animate and control main.swf, how can I access the movieclip instances inside of main.swf from my class (Content.as)

If I take out the shell and just pass the stage element from TemplateBase to Content everything works fine, but when the shell is used (I have to use it) then I get errors.

Any suggestions?