How about this at the top of your page?
You don\'t want it to run on \"this.domain.com\" (or \"www.this.domain.com\" or \"THIS.domain.com\" etc.) but you do want it to run on \"www.domain.com\" or any other subdomain, right? So this works:
$exclude = \"this\";
$host = strtolower($HTTP_HOST);
$host_parts = explode(\".\", $host);
if(in_array(\"$exclude\", $host_parts))
{
$do_the_script = \"no\";
}
else
{
$do_the_script = \"yes\";
}