Network Neighborhood thru network Subnet

I am putting in a new network which will be broken down into different subnets for different locations
eg Site 1 – 192.1.1.1
Site 2 – 192.1.2.1
Site 3 – 192.1.3.1
Each location will be connected via an ACT router.

When I click on network neighborhood when on a PC at Site 2 I cannot see any of the PCs at
Site 1 or Site 3.

Is there anyway I can configure the network so i can see all PCs no matter what subnet I am on.

Thanks
colin_berg@mcwilliams.com.au