[Thunderbird8]

You won't be able to do this with vB functions, as they only target the database that is configured in config.php. If you include vB files, you will still be able to get to the configuration parameters that you'd need to get to the database server, but you'd have to use stock PHP functions to execute queries on another database.

Of course, I could be wrong, but the only possibility I see of using vB functions in this way involves a rather convoluted method, to which you'd probably be better off with the standard functions anyway.