Data Grid View with added check box

I have a dgv that I have added a check box to the grid. I have discovered that even though I see the check box on the screen it is not really there until I refresh the screen. When I loop through the dgv the first time, I will get the message "Object not set to an instance of an object" when it hit this added column. If I refresh the screen I do not get this message. Is there some sequence I need to follow so that  a checkbox can be added to the dgv and then have the screen refreshed upon initially opening the form? This is VS C#. I think I am missing something when it comes to understanding what happens behind the scenes when a form is initially presented.