AppleScript to stop current backup, eject Timemachine disk. My Timemachine disk has another partition, so this is ejected also. Notofications is displayed when disks are ready to be disconnected.

eject_timemachine.as

-- Stops current backup
do shell script "/Applications/'Time Machine.app'/Contents/MacOS/'Time Machine' 3"

-- Set disk names
set wd to "WD"
set timemachine to "TIMEMACHINE"

-- Eject WD
tell application "Finder"
	if disk wd exists then
		eject disk wd
		display notification "WD disk has successfully been ejected" with title "WD ejected"
	else
		display notification "WD disk was not mounted" with title "WD not mounted"
	end if
end tell

-- Eject TIMEMACHINE
tell application "Finder"
	if disk timemachine exists then
		eject disk timemachine
		display notification "TIMEMACHINE disk has successfully been ejected" with title "TIMEMACHINE ejected"
	else
		display notification "TIMEMACHINE disk was not mounted" with title "TIMEMACHINE not mounted"
	end if
end tell