Press Two key at a time

1

How can I use two key at a time :

I wrote this code for single key …

stage.addEventListener(KeyboardEvent.KEY_DOWN, moving);
function moving(event:KeyboardEvent):void
{
    if (event.keyCode == Keyboard.RIGHT)
    {
        ball.x += 5;
    }
    if (event.keyCode == Keyboard.LEFT)
    {
        ball.x -= 5
    }
    if (event.keyCode == Keyboard.UP)
    {
        ball.y -= 5
    }
    if (event.keyCode == Keyboard.DOWN)
    {
        ball.y += 5
    }
    
}

but I want to use two keys at a time :-
for example:

right + down
right + Up
Left + down
left + Up

so how we can do this thing in AS3.0 ??