In order to do this effectively, what you need to do is to create a new role that you want user to be a member of. You can create this role using the OfficeClip Setup. Now go to the database and list the content of the roles table. Note the value of the role_id (which is a unique key).

Now go to the stored procedure InsInviteMemberSP (in file Sql\Queries\invitemember.sql) and at the bottom of the stored procedure add the following code:

 insert into userroles (user_id, role_id) values (@userId, <roleId>) -- where <roleId> is the value of the role_id that you found above 

Please note that this is a patch way of doing it. If the role is deleted in the future, you may get error when running the stored procedure. A better way of doing is to create a feature within OfficeClip to do this. That I guess is a topic of different discussion :)