[NAME], NetWorker gives you an option to backup only certain vmdk or the entire VM with all attached vmdk's/disks. So what you are trying to achieve might not be possible with the current version of NetWorker. Your best option is an agent based backup.
I need help with  VM backup without RDM drive , only c: drive and system state. Need steps to configure. Any help will be appreciated. 
VM backup without RDM.