Installng backtrack through ubuntu

I presently have ubuntu on a cd and I was wondering if it was possible to install Backtrack 4 through it on a usb.

Thanks in advance :D

Well I have installed BackTrack on a USB from Ubuntu, although admittedly I wasn't booting Ubuntu from a CD at the time. Im sure its possible, as long as you can access the BackTrack 4 ISO from some locally accessible storage...