Configure privoxy to use specific network interface

[Amra]

In ubuntu I am connected to network using two network interfaces.
One interface is used primary. I would like to configure privoxy to use the second one.

AFAIK I have to route all privoxy packets via specific gateway, but I have no idea how.

Forward directive in config file is just for forwarding it to another proxy and therefore it's not usable (I think).

Any help appreciated