Display no of days from Two AjaxCalenderExtender Values

Question

Sir,

 I need your help in finding the no of days from the selected value of two

 AjaxCalenderExtender into a TextBox.

 See the screenshot below:-

 
  There are two AjaxCalenderExtender Controls, one in CheckInDate textbox and other in     CheckOutDate textBox.

  I want to display the value of CheckOutDate - CheckInDate  in Total days TextBox immeditely after I select  a CheckOutDate. How can it possible?