Service Now - Business Rule

Hi, I am looking to create a business rule on Service now for the following: We’re looking for something to monitor group memberships being changed. If a user is being added to a group, and that group has the itil role assigned to it, and the user doesn’t currently have the itil role, the insert in to the sys_user_grmember table. You’d do that by developing a Business Rule. If the user already has the itil role and they are being added to a new group also with the itil role, they should be allowed to get set up. If they are blocked, only someone with the admin role can assign the license to begin with. Can you help with this? Thanks, Rayhan