RQ: refer mod

[n0kS]

hello, I have a propose for a mod that some user can refer friends and the number of registered users and their usernames appears in the users profile
example: ?action=register;sa=koko or ?action=register;sa=1 (1 is the userid) and when someone registers from that url (refered url) the username from the registered user to appear in the koko's profile like this:
Refered users: k1k1, k2k2, k3k3
Refer's url: LINK TO REFER

can this be possible?
thanks

edit: sorry for my english