An autonumber is a long variable. That's an integer, not a string. So it doesn't contain a dash. And after 20109 comes 20110. So it needs more than meets the eye.
You define a autonumber key. That's just a meaningless number. And you define a key as you want it. Then in the form that's being used to enter the record add a procedure that calculates and fills your own key. In fact, I've done so in an application I wrote last year at my work. Wanna buy it?
Kees
I am trying to create an autonumber, but i want to modify it. I work for a family owned business in the service industry, and we need a database for all the quotes for the jobs we do. i would like the primary key to be a number that shows the year the quote was issued, then an autonumber. for eg. 2010-001 or 2010-1. so that at the beginning of every year it starts back at 1. is this just wishful thinking? or is it possible? please help. i have access 2007 running on vista. thanks in advance.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic