How to add ComboBox in DataGridView Column in Windows Forms Application

Dear Sir I require to Create a New Row in DataGridView with a DropDownList of Items. After selecting a Item Rate should be filled from Item Master . After that when I input the Quantity ,  Amount should be calculated automatically. Also a new row should be generated automatically or by Button Press. When Save the Button the list of Items with <pre>Quantity </pre> and <pre>Amount</pre> should insert into a table. <pre>Select Items    Items           Rate    Quantity  Amount DropDownList         INJ Charges IM    30    2        60 DropDownList         X-RAY            250    1        250 DropDownList                                            Total Amount         310                  Save                 </pre>