[iBook] wake up and back up to me

[Matt]

I want my iBook to back up to my MyBook firewire'd external hard drive 
in the middle of the night, and set the schedule on the My Book software 
up to do that. However it doesn't work - I assume because the iBook, 
like me, is (almost) always asleep at 3am when I've set it for.

Is there a way round this? Would the scheduled start up function in 
System Preferences do it? Or doesn't that work for sleeping, as opposed 
to switching off?

cheers

Matt