hi,
Yes You already explained in my 1st 1st post and I understand that CB can not deal with authorozations.no problems.
now, the way to "give access" or not to an article / module /whatsoever is the fact belong to a group ( or not )
I can not use a regulary check of the belonging of a group. I need to do it each time a user click on a "ressource".
The fact to modify dynamically the groups allows the equivalent of group belonging.
let's put aside my previous full explanation and focus on CB features / capabilities :

1 - user click on a ressource ( article / module / whatsoever )
2 - an auto-action is trigered based on1
3 - auto action check groups belonging
4 - based on an external update , groups are updated
5 - from my understandind, it requires user reload
6 - user access the ressource ( or not )

So,I'm sure CB cando the dynamic assignement ofgroups ( already did this, with a more simple usecase ). I have my updated list of group available in session variable as exemple . now the question is how to get the auto-action triggered ? what is the best option / is your suggested previous joomla event is not good finally ?
thx

Thanks Krileon,
The trick was that I did not have the plugin enabled in the general plugins.
Regarding now : "Your usecase just doesn't make any sense", without explaning you my entire usecase which will be very specific to myself, I can give you many examples , like the "sudo" command as exemple, which require elevation of priviledges for just one command and goes back to previous level ( or after a short period).
Another exemple is on a bank account where you want to make a transfer : above a trigger amount, you need a new auth to be granted to perform the wire transfer or an amunt of time.
The usage of the groups will fullfill this requirement : if authenticated correctly, I will give the belonging to the group for 1 action ( or more ) and/or a time period. Then, I will downgrade the user to his "non priviledged" level. Make sense for you now ?
Thx

Thanks a lot !