On Sun, 18 Sep 2011 20:32:20 +1000, "Roger Dodger" wrote:

What about
enter this in C1
=($B$1-A1)/365.25

B1 is 1-9-11
A1 is date of birth
change format in column C to number with 1 decimal place.

According to the OP, a person has to be a certain age as of Sep 1. Using your method, someone who is born on 15 Sep 2000 would show as being 11.0 years old. Since his birthday would not occur for another two weeks, he would be shown as being eligible for sports when he was not.