Seems you would need a client and a server. The client would run on your workstations and add files to the queue depending on if that user needed the file now or could wait.
Have you checked out just using something like getright on your workstations?
-Mark Adams www.bitserve.com - Secure Michigan web hosting for your business.
Only host still offering a full money back uptime guarantee and prorated refunds.
Offering advanced server management and security incident response!