uses
  XMLIntf,
  XMLDoc;

function XMLChange(markup, ePath, aName, aValue: String): String;
var
  doc: IXMLDocument;
  nl: IDOMNodeList;
  i: Integer;
begin
  doc := LoadXMLData(markup);
  with doc.DOMDocument as IDOMNodeSelect do
    nl := SelectNodes(ePath);
  for i := 0 to Pred(nl.length) do
    with nl.item[i] as IDOMElement do
      setAttribute(aName, aValue);
  Result := doc.XML.Text;
end;