Help with a text processing script

[big rock candy mountain]

Hi,
A newbie to flash all assistance welcome!

I am having problems writing simple script that

1) Takes input from the keyboard
2) Checks the input against a specified string (including formatting chars)
3) If the input matches the current letter within a string then display the char in a text box.
Else play a .wav file.

I am able to trigger a .wav file but am struggling with the 1-3.

Hope someone can help

[blitzzz]

 
myListenerDown = new Object();
myListenerDown.onKeyDown = function () {
 if(Key.isToggled(Key.CAPSLOCK) || Key ==(Key.SHIFT)){
  capsOn = true;
  }else{capsOn = false;}
 
// change character to upper or lower case
 if(capsOn){
  lastKeyPressed = chr(Key.getCode());
  }else{lastKeyPressed = chr(Key.getAscii());}
 
//check to see if the key pressed is in string 
if(checkString.indexOf(lastKeyPressed) > -1){
  my_text.text = lastKeyPressed;
 }else{//play .wav file}
}
 
checkString = "AbCd";
var capsOn = false;
 
Key.addListener(myListenerDown);