Rex has indicated to me that the above is already possible in TCC, but he didn't tell me how to do it. Yes, "%@FilesSize[/S *,b,a]" will return the total allocated size of all of the files in the current directory tree, but that number is not the total size of the directory tree because it doesn't include the allocated size(s) of the directory "files" (for want of a better term) themselves (which, of course, are not really files and therefore not counted (as far as I can tell) by '%@FileSize"). How does one determine the total allocated size of a directory tree, directory "files" as well as the files themselves? The point is to know whether a given directory tree will fit on a flash drive of a given size/what size flash drive is needed to hold a given directory tree.