Is it possible to restrict search in Assigned To firld to the team associated with RTC custom categoriy

1. We have multiple teams defined under RTC project area (RTC 5.0.2iFix20).

2. We defined specific Categories and associated them with specific teams.

3. Area  Responsible field for the defect workitem is associated with the Categories. Once specific category (team) is selected from Area  Responsible field – Assigned To field displays values associated to the values from the specific team.  However if we type the name of the user not associated with this team we still able to find a name a save a defect with this name in Assigned To field with a small warning near this name saying that this user doesn’t below to the team selected.

4. Question: Is it possible to restrict Assigned To field for users from specific team selected in  Area Responsible only (meaning if any other user name is typed in manually into search – nothing will be returned).  

Thank you.