ISP overwrites resolv.conf

[T Harpster]

I'm using OpenBSD as my router.
WAN is set to autoconf in it's hostname.if file since my ISP has a dhcp
server upstream and
I don't have a static IP address so I am stuck using dhcp.
The problem is I cannot choose my upstream DNS servers, resolv.conf is
overwritten with my
ISPs DNS servers.
Is there a way around this so I can use whichever one I would like to use?