Proxy server settings ignores the URL redirect

[DL7BJ]

I want to redirect to URL on a local webserver to display a message, if a virus found.

I entered this link to proxy server settings / Antivirus / Redirect URL
http://proxy01.domain.local/virus_trojan_worm.html

But I get always the standard page, pfSense calls the PHP script squid_clwarn.php, but not the redirect URL.

How can I show our own messages?

Thanks
Tom