banner parser script

Hello, I run a small dedicated server where cpanel WHM is ran from the backend. I am looking for some kind of mod where i can parse an ad into all virtual hosted accounts on the server of my choice. that way I can host both free and paid hosting customers.

I have not been able to come across any such script which can do this. Is there a settting in apache or httpd.conf which would allow me to do this or a script I could run that would parse what I want into the peoples pages?

If you can point me in the right direction that would be great

thanks