How to restrict user from selecting date which is already selected

Sir,

dd/MM/yyyy

this is how it is displayed after i select from calender extender

in the @Page set Culture = "en-GB" for dd/MM/yyyy

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="CS.aspx.cs" Inherits="CS" Culture = "en-GB"  %>

Sir,

What will that do?

By default the format of date is mm/dd/yyyy hence changing culture will make it dd/mm/yyyy