Private Sub TreeView1_AfterSelect(ByVal sender As Object, ByVal e As _
  TreeViewEventArgs) Handles TreeView1.AfterSelect
        Dim tn As TreeNode = TreeView1.SelectedNode
        Dim ndText As String = tn.Text()
        Select Case ndText
            Case "KV-Abrechnung"
                Dim KVAb As New KVAbrechnung.KVAbrechnung
                KVAb.ShowDialog()
            ...
        End Select
    End Sub