There were threads long ago with RX, but I cannot remember if there was a solution with it. I think that there was though.
As far as Melodyne, SONAR uses ARA (Audio Random Access), so that is the preferred method to use Melodyne in a project. Typically, you will want to split and bounce clips so that you minimize the data accessed by Melodyne; then to launch it, you can either create a region FX, or use CTRL-M. When finished, bouncing that clip will render Melodyne edits into the project directly.