logout Postgres from MS Access (ODBC) ?

Hi!
In MS Access/PostgreSQL combination I have login form. After user writes all neccessary inputs and push the button, a startup procedure creates DSN-less
connection string, receates all linked tables and change connection string in all pass-through queries. It works nice...
But, how to achieve LOGOUT ? I would like to allow users to login/logout consecutively from MS Access front-end without need to close front-end.
I tried to perform new login with the same login form after already being login, but it seems that Access accepts even wrong passwords after connection
once established (!?) It seems that consecutive login does not affect at all, after ODBC connection was once established...If you give correct username, new DSN-less connection will be accepted even if the password is wrong...tabledef.RefreshLink didn't help...
So, I think that I have to close all ODBC connections (linked tables, pass-through queries) somehow and the enforce new login. How to do it ?

Also, I tried to use pg_shadow system table for inspecting whether password is OK, but it seems that password is encrypted, so Access can't compare password from pg.shadow and password on the login form. What to do in order that Access can see actual password from pg_shadow ?

Thanks.