PROBLEM WITH DUPLEX

query spain

HELLOW
DUPLEX DOES NOT WORK, WITH THE FOLLOWING CODE I TRY TO CHANGE IT IN RUNTIME , BUT IDEA DOES NOT WORK

WHY ?

  case Fconfig_impresora.cbduplex.ItemIndex of
    0:
      fr.pRintoptions.duplex := dmnone;
    1:
      fr.pRintoptions.duplex := dmsimplex;
    2:
      fr.pRintoptions.duplex := dmvertical;
    3:
      fr.pRintoptions.duplex := dmhorizontal;
  end;
  try
       TfrxReportPage(fr.Pages[0]).duplex :=  fr.PrintOptions.Duplex
  except
       TfrxReportPage(fr.Pages[0]).duplex :=  dmnone;
  end;