Second what these guys are saying. You could possibly use Melodyne wired in real time, but the latency would be a bust. Didn't even know that Melodyne could be used this way. Better for post processing and fixing screw ups after the fact.
There are convoluted instructions how to convert audio to midi, DAW specific on the JamOrigin page. Have to come out of the closet and face the collective wrath, but have only done this in Reaper. Think there is a Sonar workflow in there somewhere.
Audio to midi from an acoustic guitar thru a mic is possible however. Less than 7 ms latency on a fast system, so you can convert in real time without too much slapback. The software is revolutionary because it can take a barrage of scrambled audio data and filter out the fundamental for midi transposing.
Outside of going with a Roland hardware rig, Midi Guitar is as good as it gets, current state of the art.
http://jamorigin.com/products/midi-guitar/ John