Visual Basic.NET Programming. Beginner : How to Calculate total selected cells in Datagridview

[@தமிழ்வழிகற்போம்]

Sir I need a query.. I need to declare that Jan -mar, Apr - june, July - sep, Oct - dec as quarters of a year. And while i input two dates in datetimepicker1 and datetimepicker2 output would have come as how many quarters in those period as I declared above like jan - mar.. Pls help.