How to create a "dynamic" gate (reversed side-chain)

Hi,
Since Pentagon is not part of SONAR anymore, I have to deal with a live without vocoder effects. Not funny.
I tried to send a signal via patch points to different tracks and used the EQ to isolate specific frequencies. This is working great - I am able to re-create 15 vocoder analysis bands. The next step will be to control the carrier.
As carrier I am using an audio signal from another track.
Now my problem: If I am using sidechain of the PC-compressor, I have exactly the opposite effect. The carrier signal will be smaller at higher analysis volume. If I try to do it with a gate, I can't control the amplitude (bad english? I mean how loud the carrier signal is).
Any idea?
BTW: Yes, I need 31 tracks to recreate a vocoder effect. 17, if I reduce the number of bands to 8. So, if I overlooked a "Vocoder-Button" in Sonar, please let me know....