Problem with Shell Script Command

Hello everybody🙂 I'm using an old macbook and I encountered an issue with the ethernet: i don't know why but Snow Leopard cannot detect the Ethernet Board Mac address. So I wrote down with some help a simply sudo command to change it with the right one (which I got by Linux partition) and so the ethernet goes. My question is: what con I do to make the OS launch the command at startup "silently"? Without the password request typical of sudo and (maybe) without terminal windows launches? Thanks in advance for your help