displaying data from gridview ASP4.0 - C#

Question

hi
i have a panel having grid view with only tow columns one is CHECKBOX and other is id, need to show data on right side of the grid of the specific row on selecting the check box C#
i have populated  the datagrid and added a templeta control  as check box i have also fired this event on checkbox changed
GridView1_SelectedIndexChanged1
one it comes to get the value of specifis cell throwing me exception "object refrence not set at the instance of..... use the new key word"
any fruitfull suggestions
thanks in advance