We have a library on our web site that allows you to use part of the main flash for data storage of variables. It allows you to write over and over a one byte value. Once the block gets full you call a function and it compacts and copies the data to a second block while erasing the original block. This gives you functionality that is like byte erasing, but really it is block erasing. It needs two flash blocks reserved for the data though.

Go to:

http://www.esacademy.com/faq/progs/flash.htm

and look at the Flash Variables library.

Andy
Embedded Systems Academy
support at esacademy dot com