How to startup from CD, if CD not in drive?

i bought a brand new Mac Pro, and i have not turned it on yet.

on my first power-up of this machine, i want to startup from my system CD (instead of the internal system drive it shipped with)

how do i do this, since the CD is not IN the machine at present, and i have no way to open the tray w/out starting up the machine

i.e. if i hold down "C"with no CD, will the drive open to let me insert the CD OR will the machine default to the built-in HD instead?