[Logician]

The easiest way would be to find an host that allows remote connections to MYSQL. You would be most comfortable with this solution. But if this is not an option for you, you have to write a script that submits info in "POST METHOD". Just make sure to add 2 more fields to your default vb new thread form and add username and password there. Of course username you provided should be allowed to access this forum. This should solve the problem if you are trying to create threads by a single poster id.

But if you are trying to move threads of different users with their own username, well this would be still possible but harder to explain how (Summary: A new (an alternative newthread.php) script should be written to accept the sender scripts requests)