Limit user ads by User Roles
Does anyone know if it's possible to limit the number of ads a user can place by configuring User Roles in Wordpress? So for example, 'Subscribers' can place only 1 advert and 'Contributors' can place unlimited ads. Under 'Users' in the Wordpress menu I can see the total number of Ads each user has placed, I just need to be able to limit it, depending on their role.