Ajax :: Show Region If Option Selected

I have a PHP form, with a Customer Select List. Once an option has been selected, the 'custid', is passed to Javascript that collects all the contacts linked to that customer and populates another Select List. This works fine, but what I'm after is an extra two inputs to appear when a particular customer is selected, but I'm not entirely sure how to go about it.

Here it goes:
Table/Form:
Code:
<script type="text/javascript">
var ajax = new Array();
function getTextList(sel) {
var Customer = sel.options[sel.selectedIndex].value;
document.getElementById('text').options.length = 0;
if(Customer.length>0){
var index = ajax.length;
ajax[index] = new sack(); .....