Hi,
I tried some code for it check it...
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script src="Scripts/jquery-1.4.1-vsdoc.js" type="text/javascript"></script>
<script src="Scripts/jquery-1.4.1.js" type="text/javascript"></script>
<script language="javascript" >
function chng() {
document.getElementById("txtname").value = "*********" + document.getElementById("txtname").value + "*******";
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<input type ="text" id="txtname" onfocusout="chng()" />
</div>
</form>
</body>
</html>
Here I used javascript
I hope my quess is right in your question.
All the Best