If you try to change form element (e.g. input) value using val() function, input.change() event is not executed.

Bind doesn't work either.

Simple example:

<form>
	<input type="text" id="text" />
	<button id="button">change value</button>
</form>
<script type="text/javascript">
$(document).ready(function() {
	$("#button").click(function() {
		$("#text").val('New value');
		return false;
	});
	$("text").change(function() { alert('Event!'); });
});
</script>