1) Lux is the slick way to go, but here is the only alternative to I know of.
http://www.petertorpey.com/tutorials/volume_light/
Click on the link at the bottom of the page, the second to last sentence is the "Download the script" link. Put the .jsx file into the AE Scripts Folder. An earlier user of this had rendering problems,
http://forums.creativecow.net/cgi-bin/new_read_post.cgi?forumid=2&postid=88...
when he copied the Script Text file with his Safari using "Copy File", he got "funny little text objects" between each line of the expressions, when he deleted these everything was OK. I just downloaded the .jsx like I said and all was fine.
This is the only soution I know of for the Luxless.
2) Or you can try CC Spotlight, and put the
