Help with javascript code

Here you go, give this a try: http://jsfiddle.net/3KNnL/1/

I've got no idea where or how you'd like to create/display the added box, so I've added a function that will fire when you select the Paper option from that Select element. Hope it gives you an idea of where to go. You'll have to add a hidden input element somewhere that you make visible, or create an element dynamically and add it to the DOM
Using something like:
Adding

var newElem = document.createElement('input');
newElem.id = 'paperInputBox';
someElement.appendChild(newElem);

Where someElem is a reference to an element that you've already obtained. Perhaps a td elem with an id, to make finding it easy with document.getElementById


Removing

var oldElem = document.getElementById('paperInputBox');
oldElem.parentNode.removeChild(oldElem);

I've made the following changes:
1. Moved the code from [No-wrap (body)] to [No-wrap (head)]
2. Added an event listener to the 'load' event of the window
3. Attached an event listener to the select element you nominated.
4. Checked in the event listener for the current value of the select elem. If it's "Paper" I show an alert box. You'll need to either (1) make visible a new box or (2) create a new box and add it to the document at the correct place. (Don't forget to handle situations where this extra box is no longer required. I.e if the user selects "Paper" by mistake and then subsequently selects "Real".)
lll