how to validate in datagridview using C#

Question

hello friends, well i have big problem i have datagridview which is bind from database with check boxes if i insert i selected check boxes value in database then second time it should not insert same records . do u have any idea how can i get validation of it. and atlest should be one checked before insert a record. if not then give some Exception to user hope u understand wht i want please help me guys thanks in advance