You don't mention under which context you are mounting the disk, but what about going the other way and mounting the disk with the Applescript?
I mention context because when mounting a disk with Applescript is the big caveat that if it is a network volume, and the network is password-protected, then the user name and password would have to be stored as plain text in the script for a seamless execution.
UPDATE: A bit of searching found a similar question elsewhere. Essentially, a script can be made to do this by applying the script as a Folder Action to /Volumes:
property start_date : date "Friday, September 17, 1965 12:00:00 am"
on adding folder items to this_folder after receiving these_items
repeat with aItem in these_items
tell application "Finder"
if (local volume of aItem) and (name of aItem is "[Name of Hard Drive]") then
-- do something with the drive
-- eject aItem
end adding folder items to