problem to display last id in textbox...!

i want to show last number in  text field....!

 this is my code
 
<form id="Form1" runat="server">
     <%-- <asp:ListBox id="lbxEmployees" runat="server"
                   AutoPostBack="True"
                   Rows="5"
                   OnSelectedIndexChanged="subListChange" />--%>
                  
                  <asp:Textbox id="lbxEmployees" runa ...