How To Highlight entered Characters in ASP.Net AJAX ComboBox

Hi Mudassar Bhai

I Used One Ajax Combo box.. I binded With ArryList..  My CB  Contains More than 150 records .. When User Enters Particuler KeyWord (Ex when User Presses 'K... I used below Code

<asp:ComboBox ID="cmbClientnames" runat="server" DropDownStyle="DropDownList">
    </asp:ComboBox>