rdr question

Hello!

I have a fairly simple setup with internal network 192.168.14.0/24 and one 
external IP. Gateway is running ipfilter 4.1.8.

Generally all traffic from internal network to the outside world is 
allowed, but now I need to specifically restrict one internal IP so that:

http traffic from 192.168.14.92 to 12.34.56.78 is allowed
http traffic from 192.168.14.92 to 23.45.67.89 is allowed
http traffic from 192.168.14.92 to anywhere else is redirected to 12.34.56.78

Is this possible with ipnat/ipfilter? I thought I would need something like

rdr fxp0 from 192.168.14.92/32 to ! (12.34.56.78/32, 23.45.67.89/32) port = 
80 -> 12.34.56.78 port 80

I've been reading the docs and trying some variations and it's beginning to 
seem to me that this is impossible. I hope I'm missing something obvious.

-- 
Toomas Aas