NAT from subinterface

I have a Cisco 7204 with the following scenario.
FE3/0 connected to the ISP.
FE3/1.1 connected to Cisco Switch port1 Trunk mode
FE3/1.2 vlan2 configured for Accounts dept. Connected from Port2 on the switch to another router in that dept.
FE3/1.3 vlan3 config for Admin dept.
Connected from Port3 on the switch to another router in that dept.

I want to enable NAT so that the users connected to the other ports on the switch (not part of vlan2 or vlan3) get internet access.