Add "System" to all folders without changing current settings.

SERVER 2003, 32-bit 

Due to a new backup program, requiring SYSTEM security to all folders being backed up, I need to make sure SYSTEM has full permission to all subfolders and files in the backup scope.  The problem is, some folders have inherit permissions off, and explicit permissions set.

i.e.:

Under folder USERHOME each user has a folder, user1, user2, user3, etc.  The user1 through 3 has security of Domain Admins, and the user.  

I need to add SYSTEM to userhome and ALL subfolders and files.  When I do replace, I of course loose the user1, user2, etc. permissions.

How can I just ADD SYSTEM to all the subfolders?  Is there a command line?

Thanks!