tacacs+ server

hi does anyone know of any links that talks about configuring the authorization for tacacs+ server. I'm trying to configure a tacacs+ server, that will give full read/write access to a user X, based on the ip address of the router that the user X is trying to log in to. I basically want to give read/write access to only one routers for user X and only give read priveleges for all the other the routers user X logs into. In short I'm trying authorize the same user with different privilege levels based on the router they logged into.