Date Dependant, Hiding/Showing Articles - extension or techn

[JJB]

Hi Everyone,

I am not sure if i am posting this in the right place but i am wondering if someone out there can help with what i am trying to achieve - maybe even point out if there is and extension available.

What i would like to achieve in Joomla is to automatically make a set of articles publicly accessible based on the date - i.e. list all articles a month prior to a date specified on that article
(date specified in a variable NOT the publish/creation/edit date).

Outside of this period they will only be available to registered users.

Any advice and/or ideas greatly appreciated.


Many Thanks


JB



P.S.
I know the simplest way of doing this would be manually change the publish status to public on a day to day basis but i need to automate it.