Newbie here.  I am playing a musical show score by myself on piano, so I am recording one piano part so that I can play along with it for the Overture and entr'actes to fatten them up.   The score has various measures that repeat and the measure numbers are something like 1A 2A 3A, 1B 2B 3B, 1C 2C 3C.  I want to keep the measure numbers in my project in sync with the measure numbers in the score.  
 
Is there a way to edit the measure numbers so that after a repeat like this, I can set the measure number to a particular value to match the score?
 
I'm betting there are several easy ways to do this, but the help files don't give me anything--probably because I am not using the correct search terms.  I'd appreciate any suggestions or a point to some documentation that could help me out.
 
Thanks,
 
Bruce

You are in for a real challenge!
 
Sonar, and every modern DAW that I've used, is somewhat married to the concept of linear, as in tape, as in there are seldom any mechanisms to do repeats and the like.

To be fair, it wasn't that long ago that doing this in a notation package was pretty grueling. That  part has gotten much better.
 
I've attempted similar projects, and the best bet for me was to simply record the entire piece, which of course meant that I could not really vamp. Which is why I don't do this anymore<G>!

MTI and a couple other outfits have software specifically designed to this application. I don't know why, but they have not yet made it available to the public as a tool, although it is very cool, and you get the software as part of the accompaniment packages they license.

I have to believe there are tools out there, available to mere mortals, that do this.

Way back in the dark ages (before audio and plugins and all the other cool stuff we take for granted today) you could easily do this  sort of thing in Texture and Bars&Pipes Pro, probably KCS too. Probably others as well.
 
Not trying to rain on your parade, it's just kind of a limit to the model they use.

Of course now I'm wondering if playlists might be twisted into working for this? Might have to play around!

Hmmm... you mean to rename the measures in the timeline? I do not think that can be done, but one thing you can do is use a dummy MIDI track, place a whole note (in the Piano Roll View) at C0, then copy/paste that single bar multiple times. Once that is done, you can use the Inspector (I), make sure the "Clip" tab is highlighted at the top, and change the "Clip Name" to your desire... 1A, 1B, etc. You can then collapse that MIDI Track so that only the Clip Names are view able, and then move it to the Track 1 position just beneath the timeline. If you want, you can also use the Inspector to set the colors for easier viewing at a glance.
 
When doing the above, copy/paste is your friend... since you seem to have repeats of three... do the first three, then highlight them all before copy/paste, and you can just change the A->, then B->C, etc. in the Clip Name.

Using most any DAW to do this type of work becomes problematic because of measure numbers - especially when the score simply skips measures without renumbering. In the days of computer-generated score sheets, it would seem to be a simple matter to renumber the measures before printing, but that rarely happens.
Anyway, I've found that markers are your best friend in cases like this. When tracking a show score, I place markers about every 8-16 bars - sometimes more frequently when short vamps or intros appear. The marker doesn't have to say much; "m12" or "m16" is usually sufficient. If I'm following a vocalist, I also add a word or two of the lyric.
To navigate quickly, I've used key bindings to jump back quickly to the previous marker or ahead to the next marker. (I use F2 and F3.) A Contour pad is also great for this type of maneuvering.

 Thanks for the suggestions.  
 

It occured to me after I posted the message above is to simply drop markers above the timeline (what Kronosman mentioned above), but again you will need to place (via snap to grid is easiest), and rename each one to whatever convention best suits you.