DataGridViewColumn CellTemplate Change at run time

Hi,

I have a column in DataGridView and I wanted to change the CellTemplate
depending on which row of column I am.
Like for the first row I want a TextBox and when I focus the second row I
want a ComboBox.

I have tried changing the CellTemplate of the column at runtime but I get a
invalid cast exception because I have originally created the column as
TextBox column.

Is there a way of doing this?

Thanks,
-Asfar