Well, Sandro, you'd create a plan text file with the text:
Code:
#!/bin/sh
say "SuperDuper is finished"
Save that as a file named whatever you want, in your Home folder or some other known location, with no extension. Then, open Terminal. Type:
(there's a space after the x) and then drag the file you just saved from Finder into the Terminal window. That'll enter the path to the file. Press Return at the end.
Then, set the On completion shell script to this file.
That's all there is to it!