Private Sub CheckBox4_CheckedChanged(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles CheckBox4.CheckedChanged
        Gridview.Sort(Gridview.Columns(2), _
        System.ComponentModel.ListSortDirection.Ascending)
        If CheckBox4.Checked = True Then
        Else
            Dim i As Integer = 0
            Do
                If Gridview.Item(2, i).Value = Gridview.Item(2, i + 1).Value _
                  Then
                    '??? zeile verstecken ???
                End If
                i = i + 1
            Loop Until i = Gridview.Rows.Count - 1
        End If
    End Sub