[Exim] Routers question (routing on sender)

OK, I've got the exim book, and everything has been going swimmingly,
but now I seem to hitting a brick wall.

I have a situation where I need a couple of router rules that will do
the following (seperate rules):

1. examine the IP address of the sending host and if it is in a list (a
MySQL lookup, but that part is fine) send to a transport.

2. examine the domain name of the sending envelope and if it is in a
list (MySQL again) send to a transport.

In both these cases I want to skip the rule completely if the sending
host IP is in a fixed list (this is all to do with routing to and from a
dedicated virus scanning box).

Any suggestions?

Thanks,

Blane.