most likely, many of You know a little software called "Com Port Winamp Control" - which can control winamp externally, using 4 or 15 buttons and com port. Just connect the buttons with female com-port, connect it to pc and configure - and that is all, now You can control Your player externally.
The little article to read is here
The main problem is, that You can only click or hold a button, when You want to change the volume.
But - how could we connect "round" volume controller like this:

I suppose, that there are 2 ways:
1. To change the scheme somehow
2. Or - try to create a controller, which will click on the buttons, when You roll it.
None of the above I have not solved yet :roll:
Any creative ideas, guys?