Problem blocking sites with dns


Beta member
Hi, I have set up a windows 2k3 to manage the network, I have dns setup and the users are able to browse the web, but I'm have trouble blocking sites eg I would like to redirect it to the company web site.
A "A" record is set from to,.Do I need to put a CNAME in.

I have been throwing into the deep end, seting up this server, and my level with terminlogy in dns isn't that great.

Thank in advance