Phone Number Masked Input

HTML

<script src="http://cloud.github.com/downloads/digitalBush/jquery.maskedinput/jquery.maskedinput-1.3.min.js"></script>

<label>Phone Number</label>
<input type="button" value="Turn on Mask" id="maskon" />
<input id="phone" type="text" value="" />

JavaScript

$("#maskon").click(function(){
    alert('hey');
    $("#phone").mask("(999) 999-9999");
});