Probably not a good idea, since I was also learning QT at the time and I'm sure I made a ton of mistakes and did things the wrong way.. but I will look for it and see how bad it is.

You may want to check this project out: http://qlc.sourceforge.net/index.php?doc=Features

It's Lighting control software written in QT, and they have some faders. Not looked at the source, but I expect you could some ideas from there.

Give me a couple of days to look for mine, I'm out on the road at the moment and it would be on my desktop at home.