Hi Luca,
I don't think that it is possible to store midi commands in a registration. The registration stores information about your keyboard settings.
I've written a PC program to modify the registrations of my X1 (sorry, but I don't have a SD-1 yet). Therefore I analyzed the structure of the X1 regs. The structure is fixed, e.g. 10 bytes for the name, 1 byte for right voice, 1 byte second voice, 1 byte style,... There's no room for midi commands.
I think the SD-1 has a very similar structure.
Michael