con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data" & _
          "Source=" & Pfad & "\Source_DB.mdb"
        cmd.Connection = con
        cmd.CommandText = "select Dateiname from Logfile where Dateiname = '" & _
          (datei_zerlegt(13) & datei_zerlegt(5)) & "'"
 
        Dim anzahl As Double = 0
        'Daten lesen
        Try
            con.Open()
            reader = cmd.ExecuteReader()
            Do While reader.Read()
                anzahl += 1
                If anzahl > 0 Then Exit Do
            Loop
            reader.Close()
            con.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
 
        If anzahl > 0 Then
            frm_main.btn_logfile.Enabled = True
        Else
            frm_main.btn_logfile.Enabled = False
        End If