Delphi访问网页中的下拉菜单

Delphi通过TWebBrowser浏览网页，然后访问该网页中的下拉菜单：

uses MsHtml;
procedure TForm1.Button1Click(Sender: TObject);
var
  doc: IHTMLDocument2;
  coll: IHTMLElementCollection;
  iPos, iIndex: Integer;
  selElem: IHtmlSelectElement;
  optElem: IHtmlOptionElement;
begin
  doc := WebBrowser1.Document as IHTMLDocument2;
  if doc = nil then Exit;

coll := doc.all.tags('select') as IHTMLElementCollection;
  iPos := 0; //要访问的下拉菜单的序号，从0开始为第一个
  selElem := coll.item(iPos, 0) as IHtmlSelectElement;
  if selElem = nil then Exit;

iIndex := 2; //下拉菜单的选项序号，从0开始为第一个，2为第三个选项
  optElem := selElem.item(iIndex, 0) as IHtmlOptionElement;
  if optElem = nil then Exit;

ShowMessage(optElem.text); //获取该选项的值
  optElem.selected := True;  //选中该选项
end;