If you still can speak clearly enough but expect it will get worse, you may be interested in a beta program called "Model Talker" that allows you to "voice bank" your own speech so that a voice synthesis program can speak in your OWN voice. Some links are:

http://www.modeltalker.com/mt.php
http://www.nemours.org/internet?url=.../proj2696.html
http://www.asel.udel.edu/speech/

I hope this is helpful. I am tyring it out for this week for myself and have no opinion yet if it is any good but, at least, it is free to download.

Good luck,
Steve