Out-of-the-box, metadata extraction happens from the file object to Alfresco metadata. You're asking for something that goes the other way, which is fine, but means if you cannot find an Add-On at http://addons.alfresco.com to do it you'll have to write it yourself.
To write it yourself, start with understanding how custom rule actions work. Your custom rule action, written in Java, would likely leverage the <a href="http://poi.apache.org/">Apache POI project</a>, because it knows how to write data to Microsoft Office documents.
