change the cell type of a datagrid view in runtime

[C# Programming]

hellow
i m in a prob.
i hav a datagrid which has 3 columns.All the cell in first column will be in combobox when the form loads. but when the user selects a data from the combo then the Datagridcombo must be changed into datagridtextbox and selected data will be shown in the datagrid text box.
as well as the next row will show the datagridcombo in first column.

i need solution with code snippet.

thanks in advance and sorry for poor english.

Thanks
Tanim