Externally side-chain any compressor on the master buss to a specific track?

[StrategizedChaos]

I'm trying to get Slate Digital's VBC Rack on the master buss to only hear and react to a bass guitar track via external side-chaining to compress the entire mix (bass guitar track included). VBC Rack has no native way of externally side-chaining.

Here is the effect I want to achieve: https://www.youtube.com/watch?v=ey2v8ZEjjcY&t=9m59s

I'm assuming there's some way to make this routing happen through the GUI or code, but I'm unsure how.

Help is much appreciated, thanks!