Jun, for example you can use TweenLite for that
http://www.greensock.com/tweenlite/

code to implement:

import com.greensock.*;
//…….
scroll_c._parent.onScroll = function()
{
TweenLite.to(ref.content_mc, 1, {_y:ref.mask_mc._y - this.scroll_mc.getScrollPos()});
}

Angela, to put one more instance of scrollbar to stage you will have to add mask for each content and put different names, e.g. mask1_mc, mask2_mc etc.
than when you attach scroll set different names for each scroll
var scroll1_c = ref.attachMovie(”ScrollBar”,”scroll1_mc”,1,{_x:ref.mask1_mc._x+ref.mask1_mc._width-10,_y:ref.mask1_mc._y});
than onScroll event change position of corresponding content holders
scroll1_c._parent.onScroll = function(){ ref.content1_mc._y = ref.mask1_mc._y - this.scroll1_mc.getScrollPos();
}

Laura, you can make scrolling faster by increasing you frame rate (in this case scrolling will be smoother and faster but it will affect CPU) or you can play with PageSize,McHeight and Chunks parameters (but it will make scrolling coarser)

Thanks,