Shadow project - how to create a project shadowing its primary project

I am seeking a process to create what I call a "Shadow" project, I am sure someone has already found a quick way of doing this, so I am asking if someone can direction me to a document that explains how to create such a project.

Explaination:

The "Primary" project has all of the details defining the project.

The "Shadow" project shows an "envelope" of the primary project with less detail.

When the primary project alters, so does the shadow project accordingly.

Regards