I have 2 external HDD's currently. One of them is set up as a time machine, and I use the other one to store files that I don't keep on my computer. Is it possible to set up this external so that it also backs up to my Time Machine drive, or would I have to manually move everything from the external onto my computer, then from there, back it up to the Time Machine? I'm on Mac OSX 10.7.5 for reference. Thanks!