Tree View Web Control Events

Can any one give an example for handling a tree view
web control event, inside an asp.net application?
I am able to build a tree view using this control on an asp.net web form (on
page load) but can not handle its events later on

html tag includes the reference to the event handler and looks like this:
<iewc:treeview1 id="treeview1" runat="server" Expand = "treeview1_expand">

then the aspx.vb file includes the treeview1_expand() code:
Public Sub TreeView1_Expand(ByVal sender As Object, ByVal e As
Microsoft.Web.UI.WebControls.TreeViewClickEventArg s) Handles
TreeView1.Expand
this file also includes a withevents declaration for treeview1.