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How to Change inner content of HTML?

Method 1

Called by the framework to exchange and validate dialog data.

CString szElem;

void CMyMultiPageDlg::DoDataExchange(CDataExchange* pDX){
    DDX_DHtml_ElementInnerHtml(pDX, _T("div_element"), szElem);
    CMultiPageDHtmlDialog::DoDataExchange(pDX)
}

Method 2

IHTMLElement interface

This interface provides the ability to programmatically access the properties and methods that are common to all element objects.

CString szTmp;
CComBSTR bStr;
CComBSTR bStr2;
CComPtr<IHTMLElement> pElem;

if(!FAILED(GetElementInterface(_T("div_element"), __uuidof(IHTMLElement), (void**)&pElem)) {
   pElem->get_innerHTML(&bStr);
   bStr2 = szTmp.AllocSysString();
   pElem->put_innerHTML(bStr2);
}

How to disable the Element?

IHTMLElement3 interface

Provides access to the properties and methods that are common to all element objects.

CComPtr<IHTMLElement3> pElem
VARIANT_BOOL disable = VARIANT_TRUE;

if(!FAILED(GetElementInterface(_T("element_id"), __uuidof(IHTMLElement3), (void **)&pElem)) {
    element->put_disabled(disable);
}

Reference : MSDN