Blocking single/Multiple Users to access ??

What I have, which I think I got from DevCentral: For the IP addresss you can block based on a specific IP address (/32) or subnets (/12, 24, /whatever)

when RULE_INIT { 

 set static::AccessDenied "Whatever you want to say when you deny access. "

}

    when HTTP_REQUEST {
            if {    [IP::addr [IP::client_addr]/12 equals 172.16.0.0] 
                    or [IP::addr [IP::client_addr]/24 equals 172.168.1.0] 
                    or [IP::addr [IP::client_addr]/32 equals 1.1.1.1] } {
            } else {
                HTTP::respond 200 content $static::AccessDenied ; return 
            }
    }