jquery - adding easing to a scrollbar plugin

Question

I'm using this scrollbar plugin:

http://www.baijs.nl/tinyscrollbar/js/jquery.tinyscrollbar.js

and I want to add easing to it. I've isolated what I think is the function that calculates the movement, which is:

function drag(oEvent){
    if(!(oContent.ratio >= 1)){
        iPosition.now = Math.min((oTrack[options.axis] - oThumb[options.axis]), Math.max(0, (iPosition.start + ((sAxis ? oEvent.pageX : oEvent.pageY) - iMouse.start))));
        iScroll = iPosition.now * oScrollbar.ratio;
        oContent.obj.css(sDirection, -iScroll);
        oThumb.obj.css(sDirection, iPosition.now);
    }
    return false;
};

How would I modify this to include a bit of easing?