Access end Postgres

Hello,
I am working with Microsoft Access 2003 accessing a postgres database
via ODBC.
I would like to know the best way to change the current user logged in
the database without closing my application.

I have made a module that create linked table (ODBC without DSN). If i
use it with a first user it works fine but then if i delete all the
links and then link my table with another user, when i access the table
i have always the rights affected to the first user and in the postgres
logs i can see that it is always the first user that is identified. But
if i execute an ODBC request by program with the second user (without
using the linked table), in the logs i can see that the second user has
really executed that request.
I have also executed the command "set session authorization" but it dose
not seem to work even with a super-user.

Can anyone help me on this issue ?
Thank you by advance.

--
Jone SAUBABER HARAN
HIZKIA Informatique
64100 Bayonne (FRANCE)