bind9 and listerning on ppp0

["Charlie Grosvenor" <charlie@thegrosvenors.fsnet.co.uk>]

Hi
    I have a ppp connection to the internet and want to allow people outside
my network to be able to query my dns server. How can i get bind9 on a
machine to use ppp0 as well and not just eth* interfaces.

Thankyou

Charlie