Hey Adriano,
The site is only local right now, I'll try to show you what I have.
This is the field group setup for the field: https://www.dropbox.com/s/4vi4laklebcyi3h/Screenshot%202014-02-10%2016.00.23.png
This is a product where it's been set: https://www.dropbox.com/s/g8rl8n3cd5jakhl/Screenshot%202014-02-10%2016.02.22.png
It should show up on the top of the appropriate product in the workshop area: https://www.dropbox.com/s/iuuviu8skxd5orw/Screenshot%202014-02-10%2016.02.58.png