how to move an object a fixed distance with 1 press

I am using flash cs6

This is a very simple question but after trying several time in google i am still not able to fix this.

i have a hero which walk left and right if user hold down the button and change position 5 per frame.

Now what i want is if i press a key single time (not holding) then it will go/walk normally to a fix distance( lets say x +=50 ) and stop there.

here is my code

import flash.display.Stage;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
import flash.display.MovieClip;
import flash.events.Event;


var dPressed:Boolean = false;
var aPressed:Boolean = false;


stage.addEventListener(KeyboardEvent.KEY_DOWN , keyDownHandaler);
stage.addEventListener(KeyboardEvent.KEY_UP , KeyUpHandaler);
stage.addEventListener(Event.ENTER_FRAME , gameLoop);

function keyDownHandaler(Devent:KeyboardEvent😞void
{
   if (Devent.keyCode == Keyboard.D)
   {
  dPressed = true;
   }
   else if (Devent.keyCode == Keyboard.A)
   {
  aPressed = true;
   }
}


function KeyUpHandaler (Uevent:KeyboardEvent😞void
{
   if (Uevent.keyCode == Keyboard.D)
   {
  dPressed = false;
  hero.gotoAndStop("hero Stand");
   }
   else if(Uevent.keyCode == Keyboard.A)
   {
  aPressed = false;
  hero.gotoAndStop("hero Stand");
   }  

}

function gameLoop(Levent:Event😞void
{
   if (dPressed)
   {
  hero.x += 5;
  hero.gotoAndStop("hero Move Right");
   }
   else if(aPressed)
   {
  hero.x -= 5;
  hero.gotoAndStop("heroMove Left");
   }

   }