blocking reffering IPs?

My site's currently being hammered by refferal spam. They're not doing a DOS attack or anything, just trying to get as many of their search spam sites in the refferals of my stats page (which isn't publically viewable anyway so they're wasting their time). I've discovered that all of the urls used originate from a limited IP range (the site urls are changing faster than I can update .htaccess).

Question is : how do you block a reffering IP in htaccess? I know how to block actual IPs (useless as they use botnets) and reffering urls but how do you block the IPs of reffering urls?

google didn't help

www.myfirstcomputer.com

yes because this is such an obvious thing...