Setting resolv.conf with DHCP

I have two ethernet interfaces, eth0 (wired 10/100) and wlan0 (wireless). If I boot my machine at home where I have a wireless LAN it works fine. If I boot at work (where there is no wireless lan) with the ethernet cable plugged the DHCP picks up the IP address and the default route but does not replace the resolv.conf settings. Oddly, if I do an ifdown on both eth0 and wlan0 then do an ifup on just eth0 it works. Is there anything I can do too make this work automatically? -- Craig Altenburg