Add listener to keyboard question

Hi friends, I am kinda newbie with listeners and all that stuff, so I need your help with this.

I have a form with 4 entries, and a button who sends that info to a php file who will display the stuff.

I need to know how can I create a listeners that if some body press enter, the information is send as well. The form is buried 3 layers down from the root, same for the button. I know the next code is not correct, but just to give you and Idea of what I need

PHP Code:

---

keyListener = new Object();
keyListener.onKeyUp = function ()
{
   getURL("http://mysite.com/tracking.php", "_blank", "GET");
input = "";
input2 = "";
input3 = "";
input4 = "";
}
Key.addListener(keyListener); 


---

PHP Code:

---

keyListener = new Object();
keyListener.onKeyDown = function (){
    if(Key.isDown(Key.ENTER)){
        getURL("http://mysite.com/tracking.php", "_blank", "GET");
        input = "";
        input2 = "";
        input3 = "";
        input4 = "";
    }
}
Key.addListener(keyListener); 


---

THank you man! it worked perfect!