We are using it as a Navagation menu so it does not make sens to have to PostBack when a Group or Root item is clicked.

Ok Thanks for your help. I have pieced everything together and have figured this out flawlessly. Here are the steps...

1. Set the AutoPostBackFlags to ItemClick "Off" and ItemSelected "Off"

2. Add 4 ClientSide Events. ItemExpanding. ItemCollapsing, ItemExpanded, and  ItemSelected.

Note: ItemExpanding and ItemCollapsing will call the same function.

3. The ItemExpanding and ItemCollapsing function will have the following JavaScript which will cancel the PostBack on a Header/Group Click.

eventArgs._props[1] = 0; 

4. The ItemSelected function will have the following JavaScript which will cause a PostBack on a Child Item Click.

    var id = sender._id;

    if (!sender.get_selectedItem().hasChildren()) {
        __doPostBack(id, 0);
    }

Note: You will add any ServerSide code from the Child Click in the WebExplorerBar's ItemSelected Handler.

5. The ItemExpanded ClientSide Event you can add any code to collapse anoy other open menus and the like.

Hope this helps everyone else out! :)

Also note that when you fire off anything using the ItemClick event, it seems to force a PostBack regardless of the __doPostBack('WebExplorerBar1\',\'\')', 0); and overrides the ItemExpanding event which cancels the PostBack when clicking on the header eventArgs._props[1] = 0;

The whole concept is simple. A page has 2 WebExploerBars on it. If you click the Header of any of the WebExplorerBars, a PostBack should NOT occur. Once expanded, If you click on any child item, a PostBack should occur. Also, if another WebExplorerBar is already expanded, it should be colapsed. 

Thanks Maya, This looks promising. However, how can we get the WebExplorerBar name without hardcoding it? We have several WebExplorerBar's on the page. Thanks!