not ip address

Hi all
I would like to write this sentence in iptables rule:
"REJECT everything having port #443 (httpS) as destination except
if the IP address that query it are one of 192.168.0.18 or 192.168.0.50"

I'd like to forbid httpS/443 traffic except for those two IP addresses.

I made:

$IPT -t nat -A PREROUTING  ! --source 192.168.0.50  \
     -p tcp --dport 443 -j REJECT

and

$IPT -t nat -A PREROUTING  --source ! 192.168.0.50  \
     -p tcp --dport 443 -j REJECT

But they are all bad syntax.

Would you please help me to find my mistake?
I'm running iptables v1.4.0

                             Chef de projet chez Vectoris
                                 Phone: +261 33 11 207 36
System: xUbuntu 8.10 with almost all from package install
   http://www.google.com/search?q=mihamina+rakotomandimby

$ man iptables

[...]
This target is only valid in the INPUT, FORWARD and OUTPUT chains, and user-defined chains which are only called from those chains. [...]

Also, use the filter table for filtering.

$ipt -A INPUT -s 192.168.0.18 -p tcp --dport 443 -j ACCEPT $ipt -A INPUT -s 192.168.0.50 -p tcp --dport 443 -j ACCEPT $ipt -A INPUT -p tcp --dport 443 -j REJECT

Grts,
Rob