ActionScript 3.0 :: Sprite Loader From Library Onto The Stage?

Loading a Sprite or MovieClip from the library to the Stage is simple. You just export the symbol and do the following code:

var mySp:Sprite1 = new Sprite1();
addChild(mySp)

assuming the exported sprite is called "Sprite1" and the base class is flash.display.Sprite

But what if you have many sprites and want to encapsulate this into a function with the sprite name passed as a string? What would the code in the function look like? Somehow you have to cast the string as the name of the sprite class defined in your export but I'm not sure how. I've seen a sample using the "as" keyword but try searching "as" in the help you you don't get much help.

Code:
function loadSpriteFromLibrary(sSpriteName:String)
{
//load the sprite with an exported name passed into sSpriteName onto the stage
//what would the code look like?
}