Restrict a usergroup to viewing threads from x days ago

[TJFweb]

Hi,

I'm looking for a hack that will restrict usergroups from viewing threads from a certain number of days ago.

I know that in the standard vB thread viewing options you can set whether you want threads which were last posted in 2 days / week / 2 weeks ago etc. to display, but I want to set a hard limit on this (and also prevent users from accessing such threads from the search or from links).

A good application would be for unregistered users, as it allows them to view *some* threads (as opposed to all or none) which will hopefully encourage them to sign up.

Thanks.