two gateway on one NIC, is pf route-to posible?

Hello,

The server contains two network inferfaces (wan, lan)
   internet adsl1\
   		  >--switch->ext_if FreeBSD int_if -> lan
   internet adsl2/

The network interface ext_if has an ip address adsl1 and adsl2 as
alias.
Defeault routing is set at adsl1_gw address.

I'd like to use route-to rule in order to redirect traffic from one ip
address on lan network  (192.168.2.5) to adsl2.
Here are the rules:

nat on $ext_if from 192.168.2.1/24 to any -> $adsl1
nat on $ext_if from 192.168.2.5 to any -> $adsl2

pass in  log quick on $int_if route-to ($ext_if $adsl2_gw2) proto tcp
from 192.168.2.5 to any keep state

The rules above worked fine when adsl2 was connected to ext1_if.

Is such thing possible using an alias on one NIC?

I'd appreciate some help.