Scroll bar and tree menu problem

Is there a way that scrollbar moves down automatically so that when you click a tree menu, all the subtopics listed under the main topic gets displayed? I am facing a problem in my file in which not all subtopics are displayed.

Also, in the tree, the next topic link loops back to the first subtopic instead of moving to the next main topic. But within a topic, it works fine. For example
Topic1
subtopic1_1
subtopic2_1
subtopic3_1
Topic2
subtopic2_1
subtopic2_2
subtopic3_2

When I click next topic link in subtopic1_1, it goes correctly to subtopic2_1. But when I click next topic link subtopic3_1, it loops back to subtopic1_1 instead of moving to subtopic2_1.

Any suggestions welcome.

Thanks
Suresh