Write a batch file that stops the service from a command line and use it in the "prescan process" field of the pre/post process tab on your subclient. Write another batch file that starts the service from a command line and use it in the "postbackup process" field of the same tab. this way the service will stop, scan will run, backup will run, and service will start. the documentation has more info. the batch file should be easy, just something like "net stop myservice" and "exit 0".