If I use Time Machine to back up several laptops to different partitions of an external HD (attached via USB to my wireless router), then obviously all my files from all laptops will end up being stored somewhere on that HD. If I'm working on laptop B but the file I need is only on laptop A, which is currently away from home, can I grab the saved copy of that file from laptop A's partition on the external HD? If so, is it straightforward to navigate to the file on the HD assuming I know where it is saved in the file hierarchy of laptop A? I'm trying to plan my back-up strategy. Thank you.