Most scrollbars that are available use something like the following code:
onClipEvent (enterFrame) {
_root.Results.scroll = Math.round((_y-startY)/size*_root.Results.maxscroll);
}
That's on the main MC scrollbar part - then on a button inside of that MC they'll have some additional code.
The 'Results' part refers to a dynamic text field named 'Results'. So if you wanted to scroll two of these at once. Say for example you had two text fields named Text1 and Text2 - you would have something like this:
onClipEvent (enterFrame) {
_root.Text1.scroll = Math.round((_y-startY)/size*_root.Text1.maxscroll);
_root.Text2.scroll = Math.round((_y-startY)/size*_root.Text2.maxscroll);
}
Depending on what scroll bar your using you may have to modify other parts.
The example scrollbar that I described is a fairly common way to make a scrollbar - so you should be able to find one like that.
The scrollbar I described is part of this download :
http://www.flash-db.com/Search/ - It's part of some other items but their is a scrollbar in their somewhere.