How to disable previous date in calendarextender without using client side script

I have two textboxes with calendarextender. The first textbox represents the starting date and the second textbox represents the end date.

开发者_JAVA百科The problem I have is that if I select a start date I want to disable all dates prior to the current System date, and if I select an end date I want to disable all dates prior to the start date without using any client side scripts, compare validations or range validations. I need only server side code.