Cisco Switching/Routing :: 1941 - Use One Ethernet Port (G0/0) As Primary And Other (G0/1) As Backup Interface

Here's my problem.  I'm going to be using Cisco 1941 routers at a bunch of remote sites.  All of these sites have 2 comm paths out.  Some of them have 2 IP/VHF radios and some have 1 IP/VHF radio and a copper link using Patton ethernet extenders.  From the VHF radios the data hit our MPLS network back to our HQ and the sites with copper go directly back to our HQ.  Everything ends up at a Cisco 4948 switch. The problem I'm having is that I want the routers at the remote site to use one ethernet port (G0/0) as the primary and the other (G0/1) as the backup interface.  I've tried the backup interface command but the problem is that depending on where an outage occurs the ethernet link to either the radio or Patton stays up so it never switches over. We're using OSPF as our routing protocol and I'm sure there's something that can be done with it but I'm not sure what.