//mytext_scroll is the name of the scrollbar I'm using

mytext_scroll.update();
//---------------------------------------------------------
//---------------------------------------------------------

mytext_scroll.update();              //You must update first

if (mytext_scroll.enabled == false)  //Then check to see if needed
{
  mytext_scroll.visible = false; 
}else{
  mytext_scroll.visible = true; 
};

//mytext_scroll is the name of the scrollbar I'm using

mytext_scroll.update();
//---------------------------------------------------------
//---------------------------------------------------------

mytext_scroll.update(); //You must update first

if (mytext_scroll.enabled == false)  //Then check to see if needed
{
  mytext_scroll.visible = false; 
}else{
  mytext_scroll.visible = true; 
};

mytext_scroll is the name of the scroll bar I'm using.
///////////////////////////////////////////////////////////

mytext_scroll.update();
///////////////////////////////////////////////////////////


mytext_scroll.update(); //You must update first

if (mytext_scroll.enabled == false)  //Then check to see if needed
{
  mytext_scroll.visible = false; 
}else{
  mytext_scroll.visible = true; 
};

mytext_scroll.update();

If your using dynamic text and  AS3's built in scroll bar.  Sometimes it won't activate, ie. no scrollbar.  You must update the scrollbar after the text has been loaded.  Sometimes you only want the scrollbar to show up when needed and hide when not.

Dynamic text And Scrollbar

ActionScript 3