Simple tree - only one list expanded at any time

[dimfish]

1) Script Title: Simple Tree Menu

2) Script URL (on DD): http://www.dynamicdrive.com/dynamicindex1/navigate1.htm

3) Describe problem:
Hello everyone - I have just implemented Simple Tree Menu on a site, and it works great. Thanks. However, I wondered what modification I would need to make in order to make the script collapse any nested lists when another parent <li> is clicked ie, so that only one nested list is expanded at any one time.

I am not a javascript coder so if anyone can help me with this that would be great.

ALSO: What code could I add that would append the class "active" to the currently open parent <li>?

Many thanks.