I am trying to use my passport as an ongoing backup for the thumb drive I take between multiple locations. I don't keep everything on the computer hard drive.
You could try using the WD SmartWare backup software that comes with the WD My Passport to target your flash drive for backup. http://products.wdc.com/support/kb.ashx?id=tkF4CT
However, you should keep in mind that it would need to be re-formatted in NTFS in order for SmartWare to pick it up as a target.
If you decide to do this, make sure you already have a backup of the data that's on the thumb drive, since re-formatting would wipe it.
Here's a link that explains how to perform this: http://products.wdc.com/support/kb.ashx?id=1geWUT