Creating Users

dear all,

 I am developing a client application with C++ Builder 3 to access a
Database designed with PostgreSQL 7.0.4 using a BDE alias through the ODBC
driver.

 I would like to have a form where I can add users to my users table of my
database and also create the corresponding entry to the postgres pg_user
table.

 What I have tried through the Database Explorer is the following
transaction (I use begin and commit, otherwise the parser complains):

 BEGIN;
 CREATE USER user1 WITH PASSWORD 'passwd_user1' IN GROUP users_invui;
 COMMIT;

 I check in the pg_user table but no entry is added. I execute without the
begin and the commit comands the same query in the backend (psql) and it
works perfectly. What am I doing wrong?

 Many thanks in advance and sorry for my English

 Miguel