How can I evaluate "S1" (S1.mp3) as an element?

Question

I have a Button named "Bt1P" that when I click on it, the Sound "S1" starts to play
(Note "S1" is the Linkage class specified for "S1.mp3" in the library)
This is the code that works:
Bt1P.addEventListener (MouseEvent.MOUSE_DOWN, Bt1PDown);
function Bt1PDown (event:MouseEvent):void {
    var playSound = new S1();
    playSound.play();     
But In case I want to play for example "S2" (S2.mp3) instead of "S1" (S1.mp3),
how can I evaluate the "S1" as an element?
For example I tried this code:
    var test:String = "S" + 1
    var playSound = new this[test];  // instead of S1
and it didn't work.... here is the Error:
Error #1007: Instantiation attempted on a non-constructor.
at Asmaa_fla::MainTimeline/Bt1PDown()
Anyone has a suggestion please??

Answer 1

"S"+1 would be an error waiting to be reported, mixing data types ("S"+String(1) would be better, though wouldn't make sense as a realistic bit of code unless 1 was in variable form).
But you can dynamically load a class using a string value....
var ClassRef:Class = Class(getDefinitionByName("S1"));
var  playSound:* = new ClassRef();