2 dsl connections one problem!

[nospam@dslextreme.com]

my office has two dsl connections.  i want to set up one computer on dsl A
as the vnc server.  since the company is using dsl B, what is the proper
ip address to be able to control the one server on the other connection? 
I tried entering the local IP (obviously didn't work) and the external IP.

It's probably a simple answer but I can't figure it out. Connection A is a
static IP and connected to a netgear router if this info helps.