I wasn't sure how your expression was set up because you are using the min and max functions. Can you give me a little more detail how your query is set up. In the mean time I could get 2 - 11, 12 - 21, 22 - 31 or I could get 3 - 12, 13 - 22, 23 - 32 etc.
The basic expression is
(Int(([Age]-2)/10)*10)+2 & "-" & (Int(([Age]-2)/10)*10)+12
Let me know about your query and I'll look at it some more.
Paul