Expandable Listmenu

Hello boys and girls. ?
I don’t know much about javascript so I need a little bit of help from you, guys.
I’ve found this menu which i want to use, but with a little modification: when a list expands in the menu, I want the other lists to contract, so all the time there will be only one expanded list.
Here is the link :
[url]http://www.dnolan.com/code/js/listmenu/[/url]
Can anyone help me ?

Thank you in advance ?

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