hi alan,
You need to download CPS and install it on the Backup Exec server or a server that will be hosting the CPS replication. Then you need to push out the CPS agent to the exchange server and reboot. You then can use CPS and BEWS together to repicate the exchange trans logs. This will allow that check box your checking to work.
Im assuming you know what you checking and how CPS and BEWS protect exchange.
If you have a remote agent license for Backup Exec this will be the serial number you enter into the CPS installation.
Harry