multi-level advanced subnav

Hi all.
Trying to get to grips with some multilevel subnav in WordPress (3.0) and having a few problems getting it to do exactly what I want.

Please take a look at the sample page system I have.
http://twitpic.com/27xdik

Os say I click on About. I wanted Page1,Page2,Page3,Page4 and Page5 to display. But not the children of these pages.

When I click on Page 1, I want to be able to see –
About;
Page 1 > Page 1 children
Page 2
Page 3 (but not children)
Page 4
Page 5 (but not children)

If I choose Page 5 > Page 5a > Page 5a.1, I want to see

About;
Page 1 (but not children)
Page 2
Page 3 (but not children)
Page 4
Page 5 > Page 5a and children, Page 5b, Page 5c

Does that make sense? Apoligies if not. I’ve tried the examples on this page
http://codex.wordpress.org/Template_Tags/wp_list_pages#List_Sub-Pages

but all of them seem to either show everything at the same time, or when I click on a child page, it shows the children pages and only the parent of the child page.

This plugin was ok but not quite what I needed http://wordpress.org/extend/plugins/subpages-widget/

So, anyone know of some solid code, or a plugin I could try?

It would be neat if wordpress allowed this, and at the same time, left all the css hooks in there for us to target.

Many thanks