Redirect packets -- Ipfw & iptables

Hello,

I'd like to play a MMORPG supposed to be run on windows
I decided to use crossover-games.
I installed the game without any problems. When I attempt a connection to the game server, it's impossible to connect.

I made some searches about this issue, and I learned that the game does not connect to the right address. (iftop is great if you want to monitor your networks data-flows).

I've found a work-around but it's only for iptables.
Here is the iptables chain I have to use.

Code:
iptables -t nat -A OUTPUT -d (FAKE IP ADDRESS) -j DNAT --to (REAL IP ADDRESS)
That means, redirects packets that destination is FAKE IP ADDRESS to REAL IP ADDRESS.

I made some searches about ipfw, MAC OS X firewall and Natd, the routing table. I have not been successful. Natd does redirects only addresses in the local network.

I do not know how to translate the iptables chain above to a rule for ipfw.

Can you help me for this issue?
Thank you.