SO jQuery Fiddle

Test Fiddle mainly for SO Questions jQuery 1.4.3, UI 1.8.5

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/ui-lightness/jquery-ui.css">
<div id="conversations-uCount">0</div>

JavaScript

$('#conversations-uCount').data('UnreadIDs', '1');

$('#conversations-uCount').bind("changeData", function() {
  alert("Data changed!, new value for UnreadIDs: " + $.data(this, 'UnreadIDs'));
});

$('#conversations-uCount').data('UnreadIDs', '2');
$('#conversations-uCount').data('UnreadIDs', '3');