I registered event with 'DISCONNECT_USER' instead of 'DISCONNECT_USER]' I forgot the bracket and now it works for the 1st scenario and not for the second because I was wrong with using  'DISCONNECT_USER]'||:USR in the PS and certaintly doesn't work but It give me an  idea. I will try from the client to loop through all users existing in the DB and register them with  'DISCONNECT_USER]'+Users[i]
I don't know if I can register more than hundred users in the client in case the number of users will increase in the futur. Thanks.