Hi, I've followed this discussion applying phethean's and mortendk's changes: it is exactly the solution I'm looking for. I've submitted two patches opening this feature request on Drupal.org using an additional function that I hope makes this changes easier centralizing user role control. Any suggestion / modification is welcome: I've not added uc_attribute changes yet and a "discount" role selection by admin GUI is desirable. Please reply to drupal.org issue if interested.