DataGridView with combobox as a column, which should be editable

hi all,

can any one help me write code to make a combobox editable in a dataGridview.

I'm very new to it. have no much idea.

my requierment is, as i add a row in datagridview say with 2 column [where one column will be a combobox], user should be given a option to edit the combobox and that should be added as a item in the combobox of the datagridview.

plz help me out with this.

regards..