JQuery validation on multiline textbox for character count

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JQuery validation on multiline textbox for character count
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<script src="../scripts/jquery-1.4.2.js" type="text/javascript"></script>

<script language="javascript">

$(document).ready(function() {
//Set the Variable for max length
var MaxLength = 50;

$('#<%=txtCount.ClientID%>').val(MaxLength);
$('#<%=txtprojectdesc.ClientID%>').keyup(function() {
if ($(this).text().length > MaxLength) {
$(this).text($(this).text().substring(0, MaxLength));
}
$('#<%=txtCount.ClientID%>').val(MaxLength - $(this).text().length);
});
$('#<%=txtprojectdesc.ClientID%>').blur(function() {
if ($(this).text().length > MaxLength) {
$(this).text($(this).text().substring(0, MaxLength));
}
$('#<%=txtCount.ClientID%>').val(MaxLength - $(this).text().length);
});
});
</script>
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<asp:TextBox ID="txtprojectdesc" CssClass="textbox_reg" TextMode="MultiLine" Rows="5" Width="200px" runat="server"></asp:TextBox><br />

<asp:TextBox ID="txtCount" MaxLength="3" ReadOnly="true" BorderWidth="0" CssClass="textbox_reg" Width="20px" Font-Names="verdana" Font-Size="XX-Small"
ForeColor="#ad1800" runat="server"></asp:TextBox><span class="helptext">Characters left.</span>