Boot from USB external CD/DVD drive

Hi^^
I have a laptop with a broken internal CD/DVD drive so I purchased a USB external one, it works just fine within an OS but the problem is when booting
My BIOS sees the external drive as the 'Optical Device' (it doesn't display the internal one) in the Main section of the BIOS Setup, however in the Boot section the external CD drive doesn't appear at all and it says:
1- CD/DVD drive (displays the internal CD drive)
2- HDD
3- USB memory (it doesn't show the external drive.. maybe because it says memory )
4- LAN
...
I already updated the BIOS but nothing changed

Laptop: Toshiba A100-088
USB External drive: Samsung External DVD Writer

I appreciate all advices^^ Thanks is advance^^