Strange VOIP Question

[Hal Vaughan <hal@thresholddigital.com>]

I've got a strange VOIP question, and when I've tried Google searches, there 
is too high a noise-to-signal ration, so it's hard to get anything useful 
from searches (unless someone can suggest some good terms to narrow things 
down).  For business, I have to dial in to other computers with a modem.  
These are NOT internet connections, but straight computer-modem-computer 
connections.  Whether I go through Verizon, Cavelier, or Comcast, I'm screwed 
with high costs for the extra lines (I already have 2 lines, 1 for voice, 1 
for computer, so adding a 3rd will mean re-wiring in my house, which isn't 
the big deal, but also re-wiring to my house unless I use Comcast).

One thing that would be PERFECT for me would be if, instead of using a 
"standard" VOIP client, I could use a program that acts like a modem 
(including AT commands), and lets me control it like I would from a program 
like Minicom (or from a program of my own, like using Perl to open the device 
like a file).  This program would then send the resulting carrier with data 
out over a VOIP system, the same way a voice signal would go.  I know I'd 
have to get a service like Skype-Out to dial out of their standard system, 
but it'd mean I could do more about balancing different systems without 
adding an additional 3-4 phone lines.

I'm not a C or C++ programmer, which is what I understand I'd need to work 
with any sdks for VOIP.  I have heard of a program called modemum that can 
emulate a modem over telnet, but I don't know if that would work at all as 
part of this.

So does anyone know if what I want is possible, or have any suggestions on 
search terms to add other than obvious ones like VOIP, modem, or carrier?

Thanks!

Hal