You can of course use a script to do that but there are other methods available in NW 8.2.4 ...

1. NW Admin GUI

    Changing the parameter for multiple resources. In your case,

       -  Go to Configuration > Clients

       -  Select the clients of your choic

       -  Move the cursor to the column 'Scheduled backup'

       -  Open the context menu with a right mouse-click

       -  Uncheck the option 'Scheduled backup' and click OK

2. nsradmin

    If you want to use a script, prepare a text file containing these nsradmin sub-commands - for each client:

       . type: nsr client; name:

       update scheduled backup: disabled

         ....

    Then apply the nsradmin command as follows:   nsradmin -i

    and watch the command execution.