keyboard Event: How can I only capture the modifier keys?

Hey guys,

I know that i can use event.shiftKey, event.ctrlKey, event.altKey and event.metaKey to check whether a certain modifier key is pressed or not. But these properties will return undefined if the keyIndentifier is for modifier key.

But what I want to do is only capture the modifier keys

For example,

var w = new Window("dialog","keyboard");

var textInput = w.add("edittext");

textInput.preferredSize = [100,30];

textInput.active = true;

textInput.addEventListener ("keydown", function (k){sayHi(k)});

function sayHi (k)

{

    if (k.keyName == "Alt")

    {

        textInput.text = "Hello "

     } 

}

w.show();

I created a dialog with a edit text field, what I want to do is change the text to "Hello" when the "Alt" key is pressed, but my code doesn't work.

So, how can I only capture the modifier keys without need to press other keys or click the mouse at the same time?