如何用webbrowser空间获取网页中所有框架中的网页元素

procedure TForm1.FormCreate(Sender: TObject);
begin
  wb1.Navigate('http://oa1.sihaigroup.cn:81/');
end;

procedure TForm1.btnCalcClick(Sender: TObject);
var
  doc,framedoc : IHTMLDocument2;
  frame_dispatch: IDispatch;
  o,ole_index,oleObj: OleVariant;
  i,j: Integer;

begin
  doc := wb1.Document as IHTMLDocument2;
  if doc = nil then Exit;
  for i := 0 to doc.frames.length - 1 do
  begin
    ole_index := i;
    frame_dispatch := doc.frames.item(ole_index);
    if frame_dispatch = nil then Continue;
    framedoc := (frame_dispatch as IHTMLWindow2).document;
    o :=wb1.oleobject.document.documentelement.document.frames.item(i).document.all.item('DATA_1',0);
    if VarIsEmpty(o) then
      Continue
    else
      o.value:='test';
  end;
end;