usb2 external drive gets different designations

[dave]

Hello,
    I've got a working usb2 external IDE hard drive running on a 5.4-stable
box. My problem is sometimes when i connect it it is given a designation of
da0 while other times it is given a designation of da1 or da2. I'd like to
create a fstab entry for this drive so that when it is connected it is
mounted and when disconnected it is unmounted cleanly. I was wondering if
this was possible or if not if there was a way of giving it da0 or da1
everytime the drive was connected?
Thanks.
Dave.