By using this code you have the gridview row in which the button was clicked.
in the onclick event of your button:
Button btn = (Button)sender;
GridViewRow row = (GridViewRow)btn.NamingContainer;
By using this code you have the gridview row in which the checkbox was clicked.
in the onselectedChanged event of your checkbox:
CheckBox chkbx = (CheckBox)sender;
GridViewRow row = (GridViewRow)chkbx.NamingContainer;
if (chkbx.Checked)
{
}
I cannot give a more precize answer cause I do not know whether the checkbox or the button shows the value in column 2