Select/Deselect Nodes

Question

I am facing diff Problem with Selecting Node.

When i am selecting first node,selecting but when i select the second one previous one remains same and current one is not selecting.
I don't need post back and in Button click i need to get the selectedNode that's it.

I have gone throught the articles but  Huge Javascript code is there and I also found Simple Code like.
Treeview_Data.selectedNode.value;
But it's not working For me,Can any one help.