Sub New(ByVal ParentForm As HauptForm)
    InitializeComponent()
    Me.MdiParent = ParentForm
End Sub

      With DGV
           .RowHeadersWidthSizeMode = _
                DataGridViewRowHeadersWidthSizeMode.AutoSizeToAllHeaders
          .Rows(0).HeaderCell.Value = "Mo."
          .Rows(1).HeaderCell.Value = "Di."
          .Rows(2).HeaderCell.Value = "Mi."
          .Rows(3).HeaderCell.Value = "Do."
          .Rows(4).HeaderCell.Value = "Fr."
          .Rows(5).HeaderCell.Value = "Sa."
          .Rows(6).HeaderCell.Value = "So."
      End With