[Zope] using a ZMySQL database connection object in an external method

Is there a How-To, or are there some code fragments that will help me use a ZMySQL (or a psycopg) database connection object in an external method? Given that mysql_connection is a ZMySQL database connection object, I expected mysql_connection.db.select_db('database') to work. But I got Error Type: ProgrammingError Error Value: (2014, "Commands out of sync; You can't run this command now") Any help is appreciated. cheers, Luby