If it uses a voltage control for volume as some of the modern integrated amps do, then it's possibly quite straightforward.
For a conventional amp with the audio going through the volume control there is no way of sensing the position, only audio level.
It would likely need significant modifications.
What is the amp and how is the volume control fitted? If by chance it's on flying leads a mod could be fairly simple, but for a PCB mounted control it would be more complex (unless it's a DC voltage type).
Or, do you mean just an audio level display rather than volume control position?