Adding remote host

Hi Eveyrone,
I just started using nagios and my nagios is up and running fine and monitoring our internal network. I want to add hosts on my remote branches to my nagios. All machines are windows machine.

If my branches running 40 pc behind NATed one static IP how can i add remote hosts? i.e. i am on internal 192.168.1.0/24 and going on internet through my static IP 88.97.154.240 and my branch is on 10.0.0./24 with any other external IP on main firewall.

is there any other program which can collect all local windows client data and push it through live nagios on internet? If yes, what program do i need and what ports i need to open from firewall to allow it?

i am using latest NS Client with nagios 3.0rc1

thanks,

Kiran Mistry.