I have my main bonded t-1 and then Back up bandwidth can I use the RB 100 to act as a loadbalancing router realy just want the failover feature. So if the bonded T-1 Fails it will failover to the back up bandwidth.

Thanks In Advance for your help

Sure. Put in a second static default route with a higher metric. If the first connection fails (interface down) the first route becomes marked unavailable and the fallback route gets chosen.