Create an Online Backup Solution

Until not so long ago we were using carbonite backup plan for our business clients - when they increased their costs we changed over to using a sanbox in our office and used the freeware crashplan software. This works fine for business clients as we manage the service for them and password protect the software (so they cannot access the control panel and see other clients backed up files). We are looking to offer the service to our retail clients. We have a fixed IP address and a windows server which can host the service (This is then linked to the drives where the data will be stored). We require a backup service software to be written which is similar to Mozy \ Carbonite. The client will download a file and create an account, once the email address and password for the account has been created then they select the files they wish to have backed up. Features required: - Monitoring when new files have been created \ existing changed to be added to the backup set - The ability to backup the last three versions of each file and therefore deleting any older versions - The ability for users to schedule when backup occurs and to scale down the amount of bandwidth allocated to the uploads - The ability for users to select individual files, the version number and files in bulk to restore (including setting a path for the restore to happen) - The ability to monitor how much data is stored for each users account. We don't mind if the software is written from scratch, there is other software out there can be modified (I.e opensource) or if you know of some off the shelf software you can assist with setting up \ configuring.