Programaticly adding users to reporting services

I am using forms authentication and reporting services for reports. Every time a user is added to the applications table i manuall enter the user name into the security of the reporting server and give him rights in reporting server.  THe user in the application can edit his username. When he does that it breaks his rights to to his folders because the username in reporting services stays the same. I am also running into other problems like the username might not be unique in the datbase which is okay but in reporting services it is not ok it causes a conflict. Is there any way for me to edit the username or add a new username in reporting service programaticly via store proc so that it matches with the username in my sql table? Is there a better way to handle this so there is less customer frustration nad less manual work?