unable to capture the value of selected node in treeview?

Public Sub BindTreedetails()
       treedetails.Nodes.Clear()
       Dim sql As String = "select a.zbaid,b.zbaname from brvpn.user_reviewbranch a, phasezero.zba_master b where a.empno='" & Request.QueryString("wempno") & "' and a.zbaid=b.zbaid and closedate is null and zbatype='BR' order by zbaname"
       Dim cmd As New Oracle.cls_OracleCommand
       Dim dt As New DataTable
       dt = cmd.ExecuteAdapter(sql)
       For Each dr As DataRow In dt.Rows
           Dim tvNode As New RadTreeNode
           tvNode.Text = dr("ZBANAME")
           tvNode.Value = dr("zbaid")
           treedetails.Nodes.Add(tvNode)
End sub
       Next

For Each Node As RadTreeNode In treedetails.Nodes
            If Node.Checked Then
                selected += Node.Text + ","
            End If
        Next

        tn &= "and zbaid in (" & selected & ")"