Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button3.Click
        Dim form As New Bittewarten
        Dim reader As OleDb.OleDbDataReader
        Dim kunde As Integer
        Dim ges As Decimal
        Dim rabatt As Decimal
        Dim saldo As Decimal
        Dim file As File
        Dim z As Integer
 
 
        Application.DoEvents()
        form.Show()
        Application.DoEvents()
 
        If file.Exists("C:\Tools\Rabattaktion\Umsatz.xls") = True Then
            Kill("C:\Tools\Rabattaktion\Umsatz.xls")
        End If
 
        Dim oExcel As New Excel.Application
        Dim oWorkBook As Excel.Workbook
        Dim oWorkSheet As Excel.Worksheet
 
        ' Excel datei erstellen
        oWorkBook = oExcel.Workbooks.Add
        oWorkSheet = oWorkBook.Sheets(1)
 
        'Überschrift eintragen
        oWorkSheet.Cells(1, 1).Value = "Kd-Nr"
        oWorkSheet.Cells(1, 2).Value = "Gesamtbetrag"
        oWorkSheet.Cells(1, 3).Value = "Gesamtrabatt"
        oWorkSheet.Cells(1, 4).Value = "Gesamtsaldo"
 
 
        DbConn.Open()
        DbData.SelectCommand.CommandText = "SELECT [Kundendaten aus" & _
          "Excel].[Kd-Nr], Sum(Kundenhistorie.GesamtBetrag) AS Gesamt, Sum(" & _
          "Kundenhistorie.Rabatt) AS Rabatt, Sum(Kundenhistorie.Saldo) AS Saldo" & _
          "FROM [Kundendaten aus Excel] LEFT JOIN Kundenhistorie ON" & _
          "[Kundendaten aus Excel].[Kd-Nr] = Kundenhistorie.KundenNr GROUP BY" & _
          "[Kundendaten aus Excel].[Kd-Nr];"
        reader = DbData.SelectCommand.ExecuteReader
 
        z = 2
        While reader.Read = True
            Application.DoEvents()
 
            If reader.Item("Kd-Nr") Is System.DBNull.Value = False Then kunde = _
              reader.Item("Kd-Nr") Else kunde = 0
            If reader.Item("Gesamt") Is System.DBNull.Value = False Then ges = _
            reader.Item("Gesamt") Else ges = 0
            If reader.Item("Rabatt") Is System.DBNull.Value = False Then rabatt _
            = reader.Item("Rabatt") Else rabatt = 0
            If reader.Item("Saldo") Is System.DBNull.Value = False Then saldo = _
            reader.Item("Saldo") Else saldo = 0
 
 
            oWorkSheet.Cells(z, 1).Value = kunde
            oWorkSheet.Cells(z, 2).Value = ges
            oWorkSheet.Cells(z, 3).Value = rabatt
            oWorkSheet.Cells(z, 4).Value = saldo
 
            z = z + 1
        End While
        DbConn.Close()
 
        ' datei(speichern)
        oExcel.ActiveWorkbook.SaveAs( _
          Filename:="C:\Tools\Rabattaktion\Umsatz.xls")
        oWorkBook.Close()
 
        form.Close()
 
        MessageBox.Show("Die Excel-Datei 'Umsatz.xls' wurde in" & _
          "'C:\Tools\Rabattaktion' erstellt", "Information", _
          MessageBoxButtons.OK, MessageBoxIcon.Information, _
          MessageBoxDefaultButton.Button1)
    End Sub