Dim expr As String = "((Quantity-(Quantity%60))/60) + ':' + IIf((Quantity %" & _
      "60) < 10, '0', '') + (Quantity % 60)"
    DTDatei.Columns.Add("Val", GetType(String), expr)

    Private Sub DataGridView1_CellFormatting(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.DataGridViewCellFormattingEventArgs) Handles _
      DataGridView1.CellFormatting
        If e.ColumnIndex = [Index der Spalte] Then
            Dim val As Integer = e.Value
            e.Value = (val \ 60) & ":" & (val Mod 60).ToString("00")
        End If
    End Sub

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov