int CMarkup::GetDocElemCount() const;

GetDocElemCount is only in CMarkup Developer and the free XML editor  FOAL C++ scripting.

GetDocElemCount returns the number of elements in the document. This might be useful to gain a sense of the complexity of the document, statistically. It is also a way of estimating CMarkup's memory consumption since CMarkup maintains one structure of 8 integers per element, though there will usually be additional unused structures allocated. See CMarkup Indexing Explained.