How to connect my TI-89 to my Nikon D80 to use it as an intervalometer?

My calculator has a mini-jack connection and a usb connection.
My Nikon has a remote port on the side that uses some kind of 4 pin cable
How can I connect my calculator to my remote port?

Sounds like a great project but I've never seen it done. Bonus points if you can get the rear LCD to plot graphs.

Here's some inexpensive third party alternatives:

http://www.gentles.ltd.uk/products.htm
http://www.pclix.com/pages/pclix_main.html
http://martybugs.net/blog/blog.cgi/gear/PhottixNikosDigitalTimerRemote.html