Active Directory Sync but retain asset information

We would love to remove old computers from NS7.2 by synchronizing with Active Directory.  We've heard from our consultants that if you use the built in Directory Synchronization Schedule tool, it deletes the computers.  Normally this wouldn't be a problem, but there is a asset info in NS including PO information that we don't want to lose.  Ideally it would simply mark these computers are retired rather than delete them. 

Perhaps there is a SQL query that can be run to mark any NS computers as "retired" when they are inactive for X days?