[Serusers] SER and Radius, call control question.

Greetings, I'd like to know a few things. First, can SER control whether a call is connected or not through radius? For example, SER contacts radius and radius returns whether the user is allowed to make the call or not, then SER dials out or not depending on the answer. So this could be per destination and per user, some users not being able to call to certain destinations. Is this possible? If so, could someone provide a small example. Also I'd like to know what acc_rad_request() returns, is it a bool? What is it's purpose, does it help with the formentioned problem, or is this acc_rad only to do with CDR style data dumping? Thank you.