[web2py] Adding user to a group after registration

[Chandrakant Kumar]

I'm attempting to add a user to a group , depending on the role he chose  
from a dropdown list.

for e.g., In the register form user is presented an option of choosing  
user type 1. individual 2. organisation

how do i add the user to the appropriate group depending on his selection?  
(i went through the group archives, and one solution was to use  
request.args, but i want to use single register link)