iRule Error for HTTP::respond 404

Thanks Aaron.. I see it now.. Btw just a quick follow up.. The iRule is working, I can use Fiddler and see a 404 response on the User Agent for microsoft office protocol discovery, however I'm finding that I also need to block the Microsoft-WebDAV-MiniRedir/6.1.7600 User Agent as well. I believe what I have below is correct, syntax wise but since its not blocking as I would expected I wanted to run it by this group to confirm its sound and maybe I'm looking over something else...

when HTTP_REQUEST {
   switch -glob [string tolower [HTTP::header "user-agent"]] {
    "*microsoft office protocol discovery*" -
    "*microsoft-webdAV-miniredir/6.1.7600*" {
         HTTP::respond 404
      }
   }
}

Thanks,

Bob