Scrolling Dynamic Text Smoothly

I want to be able to scroll a dynamic text box with a custom scroll bar. When the user scrolls, the text moves, but in an exponential enertia so the text starts to scroll fast, but then slows down as it gets to the point of text the user wants to read.

Example: http://www.dubko.com their news text uses this effect.

Anyone know how I can achieve this? Or a tutorial? The only tutorials out there only move the text statically.