Dim NL As String = Environment.NewLine
        Dim Titel As String = "Statusmeldung"
        'Ableseintervall Variable (Tage)
        Dim interval_days As Integer
        '-----------------------------------------------------
        For Zeile As Integer = 0 To DGVStrom.Rows.Count - 2
 
            Dim d1 As Date = Date.Parse(DGVStrom.Rows(Zeile).Cells(1).Value)
            Dim d2 As Date = Date.Parse(DGVStrom.Rows(Zeile + 1).Cells(1).Value)
 
            'aktuelles Ableseintervall in Tagen
            interval_days = (d2 - d1).TotalDays
 
            If Zeile = 0 Then
 
                Dim Meldung As String = String.Concat(NL, "erste Ablesung," & _
                  "keine Berechnung")
                MessageBox.Show(Meldung, Titel, MessageBoxButtons.OK, _
                MessageBoxIcon.Information)
 
            Else
 
                'wenn Monate = 30 Tage dann interval_days / 30
                'wenn Monatsgenau dann 3/31 + 3/30
                Dim Meldung As String = String.Concat(NL, Zeile, NL, _
                                                          "Monate: " & CInt( _
                                                          interval_days / 30), _
                                                          NL, _
                                                          "Wochen: " & ( _
                                                          interval_days / 30) / _
                                                          7, NL, _
                                                          "Tage:   " & "?")
                MessageBox.Show(Meldung, Titel, MessageBoxButtons.OK, _
                  MessageBoxIcon.Information)
 
 
 
            End If
 
 
        Next