Using My Tag from an external drive

Hi! I keep my iTunes media folders and Rekordbox database on an external drive so I can move between two computers with the same music collection, and everything works pretty well between gigging and organizing.

However, every time I connect the drive to one of the computers and start up Rekordbox, I get the same "Sync with My Tag" dialog window. I always select "Do not sync with My Tag", because I don't want to delete all the tags I have in the drive. After that, Rekordbox SEEMS to work fine, but I'm wondering if I'm missing or losing anything when I edit my tags between the two computers.

I want any changes I make to my tags to travel with the drive, and not be localized to the computer I'm using. Am I doing the right thing? If so, is there a way to make the default behavior "Do not sync with My Tag"? I'm always worried about accidentally hitting the wrong side of the dialog box and erasing my old tags.

Thanks!

UPDATE: I figured it out! The drive was being recognized by Rekordbox as both the location of the master database AS WELL AS being an external USB device for export. I solved it by moving the master database to another drive first (using Rekordbox's tool), deleting the hidden .PIONEER folder, and then moving the database back (again, using Rekordbox, not the OS X Finder.)

Oddly enough, when I move the drive from one computer to another, sometimes it still thinks the drive is a USB Export device, and sometimes it doesn't. (i.e. it doesn't always show up in the Devices menu.) But I don't get the "Sync With My Tag" window any more in either case, which is all I wanted.

If anyone knows how to tell Rekordbox to always ignore a particular drive (i.e. don't let it show up in the Devices submenu), I would be very grateful. :)