check out the following link for configuring ISDN DDR backup links using BRI`s and dialer watch :
check out the following link for Configuring DDR Backup For ISDN With Dialer Profiles :
This is fairly trivial to do using EIGRP and dialer watch. The trick is to define different "target" IP addresses for each level of backup, define a unique dialer watch for each dialer, and filter the EIGRP advertisements on the lower priority dialer so the preferred dialer keeps dialing even when connect with the backup dialer.
I've been doing this for years for several clients and except for various IOS bugs on various platforms, it works like a champ. Before dialer watch was available, I used to use BGP to provide "interesting
traffic" so I could do it with vanilla DDR. There is a white paper on my web site describing how I used to do it with BGP, the same tricks work with dialer watch.
Good luck and have fun!
Vincent C Jones