Running Application from USB Drive?

Hi,

I have a MBP and not much disk space left. I have a game 7GB in size, that I don't have room for on my primary drive. Is there any way to run the game from my USB drive?

Can I create a secondary application folder on my USB drive? Or can I run it outside the applications folder?

I don't always carry my USB drive with me, so moving the enitre applications folder to the USB drive is something I won't consider.

I don't want to boot off the USB Drive just run an application

Any instructions or links to makiing this work would be very much appreciated.

Thanks,

Bob