Want to restrict users to have Limited Access

Hi,

Want to restrict users to have Limited Access.
If I create a new user to have an access for RHN network only for downloads the Middleware & software update only....and this privilege should only on 2-3 machines registered with RHN, should not be on all the machine registered. And he can have viewed & managed the subscription only to those 2-3 machines which he belongs.

For Example, suppose I've total 10 System registered with RHN, and I've created an user "U1" ,the U1 user should n't have access or chouln't view all the 10 system regtd. with RHN, U1 user can have view only for 2-3 system which is belongs to him, & he can update or downloads the software for those system only.