If you place a mapped Content Control into your document then you can interrogate that CC to find out its relevant details including the CustomXmlPart and xPath location.
Code:
Sub GetXPath()
Dim aCC As ContentControl
For Each aCC In Selection.Range.ContentControls
Debug.Print aCC.Title, aCC.XMLMapping.XPath, aCC.XMLMapping.CustomXMLPart.NamespaceURI, aCC.XMLMapping.CustomXMLNode.BaseName
Next aCC
End Sub
Once you have that information, you can then use the NamespaceURI to identify the right CustomXMLPart and the XPath to find the right Node in that CustomXMLPart.