How make menu (wp_list_pages) “fold”

I am playing around with the wp_list_pages-tag, and I am not able to figure out if it is possible to make it “fold” when clicking pages which has sub pages.

What I am trying to do is this: When looking at the “top” page, the list of pages should look like

* About us
* Products
* Contact us

But actually “Products” has several sub pages, and when the visitor clicks the “Products” link making it the current page I want the list to “fold out” revealing the links to the sub pages. Like this:

* About us
* Products
— * Apples
— * Bananas
— * Oranges
* Contact us

If the sub pages can fold in and out in a similar way it would be lurvely. Is that at all possible?