You're going to need a program called JMRI Decoder Pro, which is a free download; the latest version of Sun Java, which is also a free download; and a computer to NCE interface device. I don't use this setup, so I have no personal experience with it, but the Decoder Pro web site should have volumes of information about what you need.
http://jmri.sourceforge.net/DecoderPro/
Digitrax makes the interface device, called the PR2.
http://www.digitrax.com/menu_computercontrol.php
I think Digitrax is coming out with a newer interface called the PR3 that will plug into the USB port, but they don't show it on their web site.