I would like to have access to ground power before the aircraft is powered up, i.e. when completing the pre-flight scanflows, the external power would be AVAIL, and ready to be selected ON. The book says hold the MENU button to activate the CDU prior to power up, but for the life of me, I cannot hold it more than about one second, then the little hand opens again. I would like to start in COLD AND DARK, but this seems to start with the ground power selected DISCONNECT. Anybody any ideas? I have tried to do my homework on this but cannot find a reference as to HOW to hold the MENU key.