Expand and collapse treeview control???

 Hi guys,
I am trying to use a treeview control in my application. From the begining I had one parentnode and several childnodes for each parentnode. I wanted to be able to close an opened node when I click on a new one and I maneged that with OnTreeNodeExpanded method. My problem is that I now need to expand my treeview so it will look something like this:
ParentNode01
          ChildNode01:1
                      GrandChildNode01:1
                      GrandChildNode01:2
                      GrandChildNode01:3
  &nbs ...