Adding an Agent with limited rights

hello,
thanks for the hints
is there an possibility to use core workflows to transfer an content of an field to an user profile field? for example if the limited agent enters an phone number in my custom field phonenumber and choose from another field an user would it be possible to transfer that phonenumber to an field in the user?
maybe i am thinking to complex but i am tryiing to reduce the ability to see data of customers for that agent type as far i can