MCD_STR CMarkup::GetChildSubDoc() const;
GetChildSubDoc returns the child position element and any elements it contains as an XML document markup string, similar to GetSubDoc but for the child position.
It is different from GetChildData, which gets the data value of the child element. The
GetChildSubDoc method returns an XML document in which the root element was the child position element in the source document.
See Subdocuments and Fragments of XML Documents.