Must change DateTimePicker value while Update the records

i have one "DateTimePicker" alongwith username, age, sex, etc so user can save the record 1st time but whenever user wants to update the record then "DateTimePicker" value should be change without chinging of "DateTimePicker" value user can not update the record. Application should msg "You have to change the DateTimePicker value"

So, How to restrict the DateTimePicker value should be change in Vb.net 2010.

Help me out.....

Neel