Limit practitioner access to client details on Web Appointment Book to their clients only

I have listed this as a problem, rather than an idea, because it poses a significant privacy breach for my practitioners, who are all counsellors and psychologists. We currently give our practitioners read only access to the FD web appointment book, but we would like to give them Full Access so they can make and change appointments. The trouble is that this gives them access to all clients in our database, rather than giving them access to only their clients. This is a massive breach of counsellor/client confidentiality rules, which means we are unable to use this functionality. Would it be possible to create a setting whereby practitioners can be given Full Access to their diary only, and Full Access only to clients who have them listed as their Default Practitioner? I.e. practitioners would only be able to view and make appointments for their own clients. We would anticipate that all NEW client bookings would come via our office. Thanks, Joanna