Only blocking certain sites from hotlinking with htaccess

Is it possible?

[madnessmotors]

I only want to block certain sites from hotlinking my images, is this possible?

[jdMorgan]

madnessmotors,

Welcome to WebmasterWorld [webmasterworld.com]!

Yes. With mod_rewrite, almost anything is possible: Introduction to mod_rewrite [webmasterworld.com]

Jim

[madnessmotors]

I read through that and tried some different things but, I couldn't figure out how to write this correctly.