baxleyb,
You should try the steps and guide at
http://lifehacker.com/software/itunes/hack-attack-share-your-itunes-music-library-over-your-home-network-230605.php . Of course make sure the steps don't violate the terms of use policy for iTunes or the music files, especially those purchased.
A key to why the steps above will work or be closer to what you want is they share the iTunes library file too. That is a key if you want a change on one computer to then appear on others. Just having the music files shared isn't enough and why the info on the Apple page isn't enough for what you want.
Let me know if you have any questions or need more information.
b0lsc0tt