That 'service' notification, agian.

Just joined. And, I haven't found the string on the silly Service !! coming up on my dash, now that I've chosen to do my own oil changes. I have an OBD II reader, but it won't cancel the display. Please don't tell me I need a $300.00 tool to reset it. Any hints?? 2001 Audi A6 Avant 2.8