Gate automation

Hi all,
 
I'm having some difficulty automating parameters on a soft synth's audio track whilst side-chaining the input from an audio track's output.
 
I've tried with both the PC gate and Sonitus gate (pre and post send) and can produce and edit the automation envelope and assign/re-assign it as normal but without it making any difference to the selected parameters...
 
I welcome your thoughts and suggestions.
 
Thanks
 
Dave