Auto change user roles

Hi all,

I have a problem i’m yet to find a resolution for.

I have a number of user roles defined on my blog. Some with more access to content and functions than others. So far i’m having to manage swtiching users between roles manually, which is both exceedingly tedious but also prone to all sorts of errors. Particularly as it is arranged so that users switch roles with reasonable frequency.

What i’d love to be able to do is assign users to one role for a limited trial period and then automatically revert to another role once a date or condition is passed and vice versa. I’m using this so that users who build up credibilty with comments are then allowed to publish their own content for a limited period.

Any help would be exceedinly appreciated.

Thanks