As Nelz mentioned already, the required symlink already exists.
FWIW, recent udev versions have done away with the /etc/udev/rules.d/70-persistent-cd.rules, and symlink only the first device detected (via /lib/udev/rules.d/60-cdrom_id.rules).
Returning to your original question
Im wondering how I can get the notebook to recognise the drive when the pc is on the dock??
are you referring to notification of DVD media, auto-mounting of data DVDs, or...?