Here is the situation:  I have a song already written with chord progressions included.  I want to bring in a loop with the kind of style suitable for the song.  Is there any way I can change the chord progressions in the loop to match the existing chords in the song?  I know I can change the Pitch of the loop, but I want to change the Chords.  I would like to be able to do it using chord symbols such as is done in Band in the Box or Jammer Pro.  Or does this amount to just an item for a wish list? 
 
I have Sonar Platinum, Win 10.  Thanks.

Are you dealing with MIDI or audio loops?

Craig, the song originally in Sonar is all MIDI (except for vocals).  If I bring in a loop either from those supplied by Sonar, or from a supplier such as Producer Loops, I am open to whichever will work as I want it to.

I'd start with the Transpose MIDI FX. It's not ideal but I think it would get you in the ballpark, and there's also the option to transpose based on rules for particular scales.