How to set "Selected" status of a radio in WebBrowser2 Ctrl?

Hi experts:
    I want to set a HTML radio to the status of selected, the html code is here:
    <input type="radio" name="myradio" value="Value1">Radio Box Value1
    <input type="radio" name="myradio" value="value2">Radio Box Value1

You can see that the two radio is unselected. I want to press a button in my program and select the radio which value="value2".
Please note:
1 They have same name because they are in one group.
2 I can set the *value* of text input box, but the "selected" status is not the value of radio. When a radio is selected, the html code will be:
    <input type="radio" name="myradio" value="Value1" selected>
3 I also want to know how to check/uncheck a check box in WebBrowser2 ctrl.

The following can set value of text input box of CWebBrowser2 m_web;

    IHTMLElementCollection *objAllElement=NULL;
    IHTMLDocument2 *objDocument=NULL;
    CComPtr<IDispatch>pDisp;
    IHTMLAnchorElement *objAnchor=NULL;
    CString strUrl;
    strUrl=m_ctrlWeb.GetLocationURL();
    if(strUrl.IsEmpty())
        return;
    objDocument=(IHTMLDocument2 *)m_ctrlWeb.GetDocument();
    objDocument->get_all(&objAllElement);
    objAllElement->item(COleVariant("Name of Textbox"),COleVariant((long)0),&pDisp);
    CComQIPtr<IHTMLInputTextElement, &IID_IHTMLInputTextElement>pElement;
    //If it is a radio box , then use IHTMLOptionButtonEelment here
    pElement=pDisp;
    pElement->put_value(CString("Value of Textbox").AllocSysString());