Hello Beatriz!
This feature was implemented in Store Manager -
see screenshot -
http://screencast.com/t/2S9klTt7Wkv
use eMail Template to modify text of message.
When you change email status - you can choose what message to sent.
See screenshot - "Notify Customer - Using Template" - see screenshot -
http://screencast.com/t/46Mmrszy in Order Section