How to define virtual IP programmatically?

I need to define Virtual IP programmatically (Perl or VB or CMD or java). I need it for temporary use, I can't use any actual IP address and I don't care if it will be accessible only from local machine.

Any help will be appreciated.

Thanks, Yan

Why not use a home-IP from the 127.0.0.0/8 block? These will all refer to your localhost.

You can there run a program to respond to incoming packets and fake conversations.

Use your hostfile to bind fake hostnames to those IP-addresses.