Admin and user passwords on UPC1DM17 for UP-CHT01 board.

Hello.
I want to protect my board from unauthorized access to the BIOS.
Setting a user password is not what I need for that way a user must enter the user password always either normal boot or entering the BIOS. On the other hand if I set an admin password is pointless for I leave a blank password so I can get into the BIOS.
How can I set a single password that only protects the BIOS access ?