Monitored folders on portable drive

I am trying to create a monitored folder on a portable drive so that my Audirvana files and my iTunes (Music) files are on the same drive. Also this would enable me to easily move my music collection to a new computer when the time comes. However, when I try to link to a folder (called “NewLocation”} created on the portable drive, I get the following message: Unable to grant permissions to “NewLocation” because it is no longer in the given location. It seems that the only permitted location is the one with the default Audirvana media folder. Not very helpful! Or am I doing something wrong?