How to force eject CD during boot

Hello !

I have a big problem. I had to reinstall OS X on my MacBook, but unfortunately something went wrong during the install. Now, while loading the system, it suddenly freezes with a sort of big graphical glitch. I can't boot from the installation disc. I... just can't boot actually.

So here I am : the CD is impossible to eject because the system doesn't boot properly, therefore I can't reinstall it.

I want to try to boot from a live USB with a linux distro on it and try to fix things out. But I tried to boot from the USB, and nothing happened.

Is it possible to eject a CD while booting ? Are there different ways to boot from an USB ? Is it possible to boot from a USB while there is a CD ?

Is my MacBook dead ? I hope not.

Sorry for the panic, and thanks in advance for your help.