Nice try but that is still not an entirely accurate age calculation. There are a number of ways to do this but in your case I would use
Expr1: DateDiff("yyyy",[bdate],#1/12/2012#)+Int("1201"<Format([bdate],"mmdd"))
for the first calculation, and change the dates for the second
Expr2: DateDiff("yyyy",[bdate],#31/12/2012#)+Int("1231"<Format([bdate],"mmdd"))
What you need to do is chack that the person was under 65 or 26 on the first of December and Equal to it on 31st so on row 1 of the criteria put <65 under expr1 and 65 under expr2
repeat for 26 on row 2.
This gives a where clause, replacing the calculation code by fieldname for brevity
Where (expr1 <65 and expr2 =65)or(expr1<26 and expr2 =26)
Brian