BIND to give different response for different AS/source IP

Hi,

In my company we have 2 FR links to different ISPs, but we're unable to
get BGP. As far as we know our local customers (let's say from 30 or so
ASes) get better response time (ping, hops) via Link1, but all the
others get better response via Link2. Is there a way to configure Bind
to respond one IP for some AS/source ip address and different IP for
another source AS/IP address? It would be just like round-robin in a
way, but should check in some external DB/file which IP address should
be resolved from a domain name for particular source.

Thanks for help,
Jacek