General info on my question:  
Map: http://www.geekforever.com/sourcerouting.htm (you may need to use IE to get zoom and all that, but it should work in *zilla browsers)
The 10.0.0.254 Netscreen 25 is the default router in my LA office for all machines
The 172.22.64.254 Netscreen 208 is the default router in my NYC datacenter for all machines
The default route(trust-vr) for the 172.22.64.x/24 network in LA is via the private T1
The default route(trust-vr) for the 10.0.0.x/24 network in NYC is via the private T1

Specific Question:
I've got a private connection between my office and datacenter which all traffic travels over, with a VPN for failover between the Netscreens in both locations.  Recently I added a route to allow all traffic going from LA to NJ to traverse the VPN (this was done by having a route in the trust VR for the specific machine that throws traffic destined for .10 to the untrust-vr where the route/tunnel takes over).  The tunnel is a routing based VPN (unnumbered tunnel interface).

The problem I have is that I'd like all traffic that originates with the .10 machine in NYC to also use the unnumbered tunnel vice going over the private link when that machine wants to send any traffic to LA.  We're having congestion issues and upgrading that link is not an option, so I'd like to leverage the VPN instead of having it sit there idle.

I don't think source routing will work here as you can't tell the source routing engine in the Netscreen to use a particular unnumbered interface or even VR.  Granted, I haven't used source routing on the Netscreens much, so I may just be missing something simple, or there may be an entirely different solution to this problem.

Any help would be appreciated.