Iptables question

[I Rattan <ratta1i@cps.cmich.edu>]

I asked about a modem dialin server problem. I saw
no response, so, I rephrase it.

The Linux box is connected to Internet on 141.209.169.x

The dialin ppp (Linux end) ipaddr is 192.168.0.10
The dialing client gets ipaddr       192.168.0.11

How do I make iptables to forward form 192.168.x.x
to 141.209.169.x (looking for rules form ppp0 to eth0)?

-ishwar