You should not try to talk across modules, if you need a master detail view you should do it all inside a single module. Its a matter of separation of concerns, a module is an entry point to a feature and features should be self contained. Features do not and should not have any knowledge or dependencies of other feature instances that maybe on the same page.
If you want to link to supporting page(s) in your custom feature you can pass the pageid and moduleid in the url to the supporting page. Study the blog or forums feature, they have supporting pages.
Hope it helps,