a way of deviding into NS records with user`s address

[三家本 恭子]

Hi,
Des anyone know how to devide reqested user into several NS record with
its source IP addresses. That is , theres are to NS recods in one
domain.
  xxx.com   IN   NS   aaa.xxx.com
                      bbb.xxx.com

If a client is reqesting to this named`s and his nework address is
1.0.0.0/8, he have to point to aaa.xxx.com. other client is  reqesting ,
he refer to bbb.xxx.com.

So I want to control and devide into several NS records with reqeting
user`s address, so that user will be able to point to nearest server
from his position.

Iam running BIND 8.x on Soralis

Thank you,