yeah, it's almost pointless to have this so called MIDI Punch In function since it doesn't really replace the wrong part. Worst of all is that you have to listen to the previous misplayed part while you are trying to record the second take. I don't know why steingberg as a big audio and midi software leader as it is can make stupid mistake or creat poor functionality like this in their top of line product.
I found a thread in their official website that talked about the same thing like we are here, which comfirmed that Cubase SX really doesn't have a MIDI Punch In function in its conventional meaning.
Sorry, i am at work and happen to have no Chinese font entry system installed. Hope everybody understands.