DataGridView Example - repost

I am using a DataGridView control in a VS 2010 C# project. I have a column of the type DataGridViewComboBoxColumn. This type of column only allows the user to select an item from the list. I would like the functionality where the user can select an item from the list or enter his/her own item. Please provide a very simple example demonstrating how to implement it. The example should be in VS 2010 C#. If you bid, please state how quickly you could provide me the example.