Subpage woes…

Hey everyone… So, I’m not sure if I’ll get all of the WP terminology correct, but the gist of what I want to learn how to do do is the following.

How can I set things up so that when I’m on any *sub-page* of *page* X, there is a list of all other *sub-pages* of *page* X listed in the side-bar of the *sub-page* that I’m on. Did that make sense? I hope so.

For instance, here’s a link to a testsite that I’m building.

http://www.testsite.tennberg.com/iep/

Right now, I have one *page* (called A) and one subpage of A (called Augustine). And here’s what I want to do. When someone is viewing the Augstine subpage of A (or any other subpage of A), I would like all and only subpages of A to be listed in the sidebar. I’d also need this to work for all other page / subpage relations (e.g. when I create a B page and various subpages of B, the same sidebar sorting takes place, except this time for the B subpages).

Anyway, I could really use some help with this.

Thanks..