Hello Vincenzo,
I realize this answer is far too late to be of use for you, but this is part of a matlab answers clean up process so I will provide a basic answer.
The model will need to be modified by hand to take this in as a simulink signal. This will not necessairly be possible with all models, however, the powergui block has a tool that allows for the customization of existing specialized power systems blocks. This would be the best way to try and modify it.
Regards,
Joel
