Creation Date relevance modifer for Anything-Digital's Advanced Site Search

For a Joomla 2.5 site. Using advanced site search from Anything-Digital.com. [login to view URL] We need an additional relevance modifier written that will allow weighting of returned search results based on article creation date. Attached is the admin backend showing existing relevance modifiers. I will provide full most recent copy of software ... but please... i only want to talk to persons who have ALREADY worked with this software. The website we're building in 2.5 has thousands of articles. We prefer a search to give a higher priority to an article with a recent creation date.. we still want other relevance modifiers, ie, keywords in title, body, etc. But an article with lower keyword density created in 2013 should show up higher in return results than one with slightly higher keyword density written in 2011 for instance. See this: [login to view URL] At the bottom of that page it says "Additional Relevance Modifiers may be added in the Relevance Modifiers area of the dashboard." but the company has no information I've found on how to do that or if a creation date modifier can be done. Again, please I only want persons who have specific experience with this particular software. Thanks