Question regarding panning

Sonar has Channel Tools for that.

Hi, the other way one could read the OP's post is that he wants strings-I panned say 10%, strings-II 20%, and strings-III 30%... to spread each section independently. I know of no way other than to do it manually....else as Adq & John already said: Channel tools or the Stereo imager from the Nomad plugins.

Thanks for all of the answers, and I apologize for not being clear.  Mostly I use Garritan instruments for orchestration, and they have a setting for front-to-back stage depth, which could simulate rows.  I wasn't thinking about panning the violas in individual sections, although that might be an option; for example, setting viola I to 30% left, viola II to 0 and viola III to 30% right.  I was thinking more along the lines of violas I in the front row in an arc from 30% left to 30% right, violas II in the second row, and violas III in the third row, in which case I would need nine viola instruments.  Quite frankly, I haven't used the channel tools, so that is intriguing.  Thanks again.

As Beepster said: check how many ouputs you have at your disposal from within Garritan. I am guessing you would be able to set/send 3 groups of violas to 3 individual audio tracks within Sonar. If so you wouldn't need 9 viola tracks but only those 3 as by your statement you are able to set the depth of an instrument (or instrument groups) so this parameter would take care of placeing violas I in front of violas II and in front if violas III.
Then use the channel-tools plugin (3x) on each group of violas to set the width and/or pan position: If you are going to need detailed control over the three groups during mixing I would create 3 busses, one for each group of violas and place the plugins in the bus, else I would place the plugins on the vst output tracks and send the three groups to one bus.

Alright then. Based on that description (if I'm understanding it correctly) try this...
 
Since you are not limited by output options set up individual Instrument tracks in Sonar (the MIDI audio outputs that will accept the signal for each voice you want from teh VSTi). Set the outputs of those tracks to whatever downstream bus you normally would (like a "Violas Solo" or simply the Master).
 
Pan the tracks however you like. You can treat these like "close" mics of the instruments.
 
On each of the tracks create a Send that goes to a specific bus. Call it something like "Violas Room" or "Violas Group".
 
You can now treat that bus as if it were a stereo mic setup in the room. You can use the Pan control on the Send modules of the specific tracks to position them where you'd like in the stereo field (doesn't necessarily have to match the virtual "close mic" panning on the main tracks pan controls). Put some reverb on the bus to create your "room/hall" or you could setup a separate parallel reverb bus (I won't go into the routing of that unless you need me to). You'll probably want convolution reverb for that. Actually if you use a separate parallel reverb bus you could also send the close mic tracks there to keep it all in the same "space" if you want.
 
Add your stereo spread VST to that bus (so Channel Tools or whatever). You may not even REALLY need this because you already have tons of panning options (on both the track and the sends) but you could constrain the stereo field to the 30-30 parameters you are describing (so you would be LIMITING the stereo field... not widening it).
 
Now you can just blend your Viola "Room" bus in with the close mic signal and tweak to taste.
 
Alternatively if ARIA player allows for auxilary bus/sends on its internal track mixer you could set up this "Close Mic" and "Room Mic" set up right inside the VSTi. Just add all the Violas to your Aux busses and make sure that the aux bus has it's own track inside Sonar (on top of the main "Close" mic outputs). That way you can use the ARIA player's internal space/depth/placement tools which might be easier to use/better suited to creating a real orchestral environment.
 
In that scenario you'd still have your "close" mic'd instruments going to their own tracks and the Aux goes to it's own track and you blend them as stated before. Any extra reverb, compression, stereo width tools within Sonar can go right on the tracks and then you can just send all the tracks to a single summing bus (Violas ALL or whatever).
 
Just some ideas. You may indeed want to play with compression in these scenarios, probably on the "room" track so the room is squashed and adds fullness while the individual viola tracks are more dynamic. Using a two stage compressor setup would probably be best due to the acoustic nature of the material so you send the signal through one compressor to tame the peaks a bit and then (maybe after some eqing) a second compressor to bring up the lower volume parts even more to fill it out. This is to avoid the "pumping" a single cranked compressor can cause... especially on more dynamic material which is really noticeable on acoustic material. That is merely an extra suggestion.
 
I am NOT a pro engineer (yet... but I read a lot) and only have minimal experience working with virtual string parts so take all that with a grain of salt. It's just stuff I would try if I were attempting what I THINK you are doing.
 
If I am way off base my apologies.
 
There is a fellow around here that goes by Konradh who does WAY more of this who hopefully will stop by as well as many others. I think Sidroe is another fellow who does this type of thing as well but I am unsure.
 
Perhaps edit your title to include something about Orchestral panning/Violas/ARIA player or whatever to signal that's what this thread is about. I'd be curious to see what some of these guys come up with (no doubt they'll point out how terribly wrong and awkward my plan is... lulz).
 
Cheers.

Thanks all!