How to set User access for certain clients

Hi every one i am facing some problems, i configured radius server i configured a client and finally i have configured a user as well how do i block or deny access for users to log certain clients as and example -- User1 can log to the SWA but he should not be able to log to SWB please help me on this , i read so many articuls but cant fiend a way to do it -- dilanka nayanajith Thank you