How to test whether a drive is a mounted drive?

I've now posted the two buttons, “Deletion“ and “Restoration“, at
[url]Ersatz Recycle Bin for USB drives and mapped network drives]

@tbone, I didn't go to a CSV-file solution because it seemed much easier to tuck the information needed into the metadata field “User Description“. It works, but it may not be the most elegant solution. I've made a few other comments about the situation in the post, plus some possible extensions to further situations.