Waiting 1/8th second to detect onKeyDown

programming flash
1

Rock Paper Scissors game - again (but soooo close).

How would one go about telling Flash “Hey, if the User does NOT hit the left down or right key within 1/8th of a second then…do something”?

Here’s my AS which works and displays a Rock, Paper or Scissors depending on the arrow key pressed, I just need some way to “time out” if they don’t press a key quick enough.

 
var keyListener_obj:Object = new Object();
keyListener_obj.onKeyDown = function() {
    switch (Key.getCode()) {
     case Key.LEFT :
      RPSUser_mc.getNextHighestDepth();
      RPSUser_mc.gotoAndStop(2);
     break;
     case Key.DOWN :
      RPSUser_mc.getNextHighestDepth();
      RPSUser_mc.gotoAndStop(3);
     break;
     case Key.RIGHT :
      RPSUser_mc.getNextHighestDepth();
      RPSUser_mc.gotoAndStop(4);
     break;
     }
};
Key.addListener(keyListener_obj);

I have no clue what I would need to search for to do this.