iptables (was port forwading)

Okay despite the fact that iptables didn't show up when I did lsmod (I
guess I forgot netfilter was part of the *kernal*). It looks like
iptables does install on RH 7.2 So I thought well instead of rewritting
all my ipchains right now maybe I can just add a iptable rule to my
firewall script (if this is vastly wrong please let me know). So here is
my attempt

iptables -A PREROUTING -t nat -p tcp -d $IPADDR --dport $WEB_PORT \
    -j DNAT --to-destination $WEBSERVER

but when I try to run my script I get this

iptables v1.2.3: Unknown arg `--to'

my man page of iptables says that --to-destination is a valid arg
though. So any thoughts??

Thanks in advance,
Carl P.