нашел
private void dataGridViewInOut_CellEnter(object sender, DataGridViewCellEventArgs e)
{
DataGridViewComboBoxCell combo_cell = new DataGridViewComboBoxCell();
combo_cell.Items.Add("one");
combo_cell.Items.Add("two");
dataGridViewInOut[e.ColumnIndex, e.RowIndex] = combo_cell;
}