If you're using AutoCAD 2000, you're in luck
You must have the Express Tools loaded.
Draw the arc first, then go to Express>Text>Arc Aligned Text. You will then see the very wonderfull ArcAlignedText Workshop dialogue box, see below:
Unfortunately, you have to pay extra for the Express Tools for use in later versions of AutoCAD but to you, they're free.
The reason you can't find any reference to this is that the Express Tools are undocumented but there is a Help option on the Express pull-down that gives outline information on using the tools.