First, in my login, there is no registration option.
I want to have a special user - that when some one is login to it it get the CB registration form (and that all for this user) ...
The system works normally to all other users ...

Does some ting like this exist?
Do I need to write a plug-ins for this purpose (something that I want to avoid)?
any other idea?

I see no way of doing this as a plugin. You need to make a hack to both CB login component and joomla core (access rights).

mikko

I also came to this conclusion...

Is it possible to remove the 'registration' option from the login form even if the 'allow registration' is on!