Help with Access List

[Perry Lucas]

Here is the scenario...   A 2600 series router is connecting multiple offices in the same location to the Internet.  The offices are seperated via VLANs on a Cisco 3500 series switch with ISL Tunk links to the router which is running IP Plus.  The IP Subnets are 10.0.1.0, 10.0.2.0, 10.0.3.0, etc with a Class C mask.  The router is also NATing the 10.0.x.0 address to a Public IP Pool.  The client wants to prevent any traffic from being routed between subnets.  (i.e. 10.0.1.0 can not talk to 10.0.2.0 or 10.0.3.0 and vice versa.)   What is the access list to prevent the subnets from routing to each other, as well as the correct access group on the sub-interface (inbound or outbound) while not interrupting connectivity to the Internet or the IP Nat pool...   Perry