QUEUES ring options leastrecent

I am using freepbx in a call center. latest freepbx, latest svn release 1.14 asterisk. the calls from the queues are being distributed to the agents with the least recent call. However if an agent walks away from the phone and was the least recent to receive a call the phone will ring without moving on to the next caller with the least recent call.

in effect i want the system to hunt the least recent agents on a call.

any ideas

thanks for your help.