I don't believe that the robot inactive message is modifiable in the probe. In order to change it, you'd need to set up a preprocessing script to modify it before being stored, or an AO profile that matched the incorrect message text and updated it to the correct text. Both will require writing code in LUA.
The CDM probe allows you to create alternative messages - look to "Setup->Message Definitions". Just create a message with the text you want. Then on the drive disk usage configuration page use that new message rather than the default. Sounds like you'll need to create a message per drive in order to get the text you want.
-Garin