Although you got the answer to your issue , i though adding some more can be benifial for the memebers foolowing this discussion thread and for future user too.
To make it more advance you can setup default value for dummy characteristic ( TEST_FC in flavio ciotola example above) by setting up default indicator in value tab of characteristic. With that user don't need to assign any value to see the pop-up message, as soon as configuration pop-ups it an pop-up message will also follow.
is it possible to increase a length of message as 30 character will not be much if some one want to use it for supplying instruction to a user on " how to completly configure a complex product"
Can we add a link in message by clicking which a detailed document stored on server can be open and show step by step guide. just an idea. 
hope you will agree to this possibilities too.
Thanks
Ritesh