Cisco Routing (2650xm)

We have 2 offices connected via T1 point to point with each office having it’s own internet connection. We’ve been hainv problems with one of the interent connections going down and I have to manually change the route in the routers to re-route internet access over the point to point T1. I cant seem to find a good how to guide or config that will have the cisco detect when one connection drops to route automatically. My cisco knowledge is a bit limited so any help would be great.
Thanks….