Hi,
There seems to be another problem with your suggestion Lynne, which is that some DDoS softwares now have the ability to bypass htaccess firewalls by simply going to the site, getting the username and password shown in the msg, and then entering them in the software itself and that would make the proxies able to enter that username and password when requesting the site! .
I guess this way is gone with the old days now, anyways , I've managed to create that firewall myelf, I'll be posting it here soon