Reply to use current from a FW port to power a USB hub??

This is a slightly bizzare question,

my macbook only has two usb ports, which is not enough for my dj needs with t scratch pro, but in order to have more USB ports i need a hub, which would need to be powered,

BUT when i turn up at a venue i only want to plug in the power supply for my laptop, SO what is the believeing on whether, with a little crafty soldering, i could make use of the currently unused FW port on my laptop to power a USB hub so i can add more control options?

thanks all!