Event for CalendarExtender

Hi all,

How can I fire an event for  asp:CalendarExtender. Is there any way to do this? I need a event when I select a date.

<asp:TextBox ID="txtDOB" 
                            Runat="server" CssClass="mytextbox" onfocus="WaterMark(this, event);" Text="Date From"></asp:TextBox><span style="width: 100px"><asp:CalendarExtender ID="txtDOB_CalendarExtender" runat="server" 
                            Enabled="True" TargetControlID="txtDOB" Format="dd/MM/yyyy"> </asp:CalendarExtender>