how to insert the tag in existing tag based on the div id using extjs?

how to insert the tag in existing tag based on the div id using extjs?

I need to insert some tag in the existing tags using extjs based on the
div id 'task123' and also display some alert accordingly.
HTML code:
<div id="task123"> <div class="msg" id="sample">
<ul class="msg-icons"> editButton </ul>
<h3>Task Details</h3>
<div>Messages</div>
<br/>
<a class="closeMessageBox" style="cursor:pointer;
float: right; font-size:7pt;">Click here to close</a> </div>
</div>
insert the the new tag in to the old tag after the
<div>Messages</div>
based on the div id task123 here is the extjs code:
var iconDisplay = {};
iconDisplay.html = '<div class="icon-right">' +'</div>';
var icondisp =
Ext.fly("task123").query('a.closeMessageBox');
Ext.core.DomHelper.insertBefore(icondisp[0], iconDisplay);
Ext.fly("task123").select('div.icon-right').on('click', function() {
alert("tested icon right...")
},_message);
The above code not working properly.