Calculating fields

Hi

At the moment I am creating a database for a football club.
The database is suppose to hold the information of all players.

All players are put into age groups as follows

Boys:
Age: Group
5 and less u5 small feets
5+6 u7 poders
6+7 u8 sand players
8+9 u10 mini boys
10+11 u12 little boys
12+13 u14 boys
14+15 u16 junior boys
16+17 u17 yngling u17 boys

Girls:
Age: Group
5 and less u5 small feets
5+6 u7 poders
6+7 u8 sand players
8+9 u10 mini girls
10+11 u12 little girls
12+13 u14 girls
14+15 u16 junior girls
16+17 u17 yngling u17 girls

The age determind which group the player is put into. What I think of doing is to make a calculating table where age is calculated via :
year of bearth - existing year = actual age ex. 1996-2007=11 => equals little girls or girl!

In the above ex. the player with the age 11 would automatical be put into the group u12.

Furthermore every player are via radio button or checkbox marked as girl or boy.

Beside the above rules it should be possible to overrule it by putting ex. a player aged 8
into group u12

Do you have any suggestion, how to solve above? Or do you have a database where the same issue is shown?

BR Dennis