I begin to understand what you need.
In the code behind a menuitem, you can do whatever you need. For instance, retrieve the message ID of the email (if menuitem is added to BlackBerry messages app), retrieve (parts of) the content of an email, and much more ...
The code to do that will have to come in the run method of the menuitem application. From there, with the retrieved information you will have to invoke your more-details-application, but I'm not sure how to do that since I'm also quite new to BB development. But there must be some info around here on how to invoke third party applications.
Did this help you, or did I miss the point?
Bye, L J