cmd.CommandText = "Select sum (gesamtpreis) as gesamtpreis,sum(menge) as menge," & _
  " from Rechnung where KdNR = @kun and  Datum between @vondat and @bisdat"
 
 cmd.Parameters.Add("@kun", OleDb.OleDbType.VarChar, 5)
 cmd.Parameters.Add("@vondat", OleDb.OleDbType.Date, 20)
 cmd.Parameters.Add("@bisdat", OleDb.OleDbType.Date, 20)
 
 Dim timex As Date = CDate(ds.Tables(dastring).Rows(u).Item("Event1"))
 timex = timex.AddSeconds(1)
 
cmd.Parameters("@kell").Value = kellnernummertemp
cmd.Parameters("@vondat").Value = CStr(timex)
cmd.Parameters("@bisdat").Value = CStr(ds.Tables(dastring).Rows(u).Item( _
  "Datum"))