help with simple script for showing diff banners depending on where the user came fro

Hi, I am totally new to this PHP stuff.

Does anyone have a script that can tell where a visitor came from and then display a different banner or image only for those users?

So if say soemone comes from www.msn.com then the banner would say something like "Welcome MSN People".

Any help would be great.
Sam

You can check $_SERVER['HTTP_REFERER'], though be aware that this can be masked/spoofed/etc. since it's populated strictly by client-side data.

But I have no idea what to do with this.

I am more of a designer rather than programmer.