webbrowse如何获取选中的文本

HRESULT   hr; 
    CComBSTR   bstrText;
    CComPtr <IHTMLElement>   pBody; 
    hr   =   pDoc-> get_body(&pBody); 

    IHTMLSelectionObject *pSelObj = NULL;

    pDoc->get_selection(&pSelObj);
    IHTMLTxtRange *pText = NULL;
    pSelObj->createRange((IDispatch**)&pText);
    pText->select();

    BSTR bstrTxt;
    pText->get_htmlText(&bstrTxt);