"dial-peer hunt" may help you.
Router(config)#dial-peer hunt ?
<0-7> Dial-peer hunting choices, listed in hunting order within each choice:
0 - Longest match in phone number, explicit preference, random selection.
1 - Longest match in phone number, explicit preference, least recent use.
2 - Explicit preference, longest match in phone number, random selection.
3 - Explicit preference, longest match in phone number, least recent use.
4 - Least recent use, longest match in phone number, explicit preference.
5 - Least recent use, explicit preference, longest match in phone number.
6 - Random selection.
7 - Least recent use.
http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/dial_peer/dp_confg.html