You need to detect when the user presses a key.
Listen for the KeyboardEvent.KEY_UP event.
function onKeyDown():Void
{
var code:Number = Key.getCode();
var char:String = String.fromCharCode(code);
trace("Key Down : code : " + code + " char : " + char);
}
Key.addListener(this);
function onKeyDownHandler(event:KeyboardEvent):void
{
var code:uint = event.keyCode;
var char:String = String.fromCharCode(code);
trace("Key Down : code : " + code + " char : " + char);
}
stage.addEventListener(KeyboardEvent.KEY_UP, onKeyDownHandler);