Reaper ReaComp can be used in RB and should do as desired. It may take a little tinkering with to set up the control track, but should not be impossible. In Reacomp it's called the Detector Input.

It's a free download for the set of free ReaPlugins.

http://www.reaper.fm/reaplugs/


Make your sound your own!
.. I do not work here, but the benefits are still awesome