Change expressions in Cisco CNR

My company is changing identification criteria for residential internet users. We need to change the way the CNR reacts to this new ID and program a SCE (Service Content Engine. This is already done. For example our CNR is configured to identify a custom DHCP option (254). Now we need to reprogram it so that if this option = NULL then look for DHCP option 82 and then read a serial number in order to pair it with a service scope.