procedure TForm1.DateTimePicker1Change(Sender: TObject);
var P: TfrxPage;
    i: integer;
    S: string;
begin
  with frxPreview1 do begin
    P := PreviewPages.Page[PageNo - 1];
    for i := 0 to P.AllObjects.Count-1 do
      if TObject(P.AllObjects.Items[i]) is TfrxMemoView then
        with TfrxMemoView(P.AllObjects.Items[i]) do
         if Tag = 123 then Text := DateToStr(DateTimePicker1.Date);
    try
      Lock;
      PreviewPages.ModifyPage(PageNo - 1, TfrxReportPage(P));
    finally
      Unlock;
    end;
  end;
end;