[Lynne]

It's going to have to be more than just a cron job since default vbulletin doesn't keep track of how long a user has been in a certain usergroup. If that needs to be done, you are going to need to add a new field to your table and also write additional code to enter the date when a user is moved into his new primary usergroup (assuming it's the primary group, if it's a secondary group it could get pretty tricky). Anyway, what I'm saying is that this isn't as straightforward as you may want it to be and it won't get done with a simple cron job.