I have two list boxes on the same page. One is populated with items from a database table. I want to be able to select an item at a time, choose the quantity from a dropdown list, then click on a button 'Add' and transfer the selected item from list box 1 to list box 2 with the corresponding quantity. I want to be able to do this multiple times. Also, when the item is added from list box 1 to list box 2, it should disappear from list box 1 to prevent the user from choosing the same item more than once. Similarly, the user should be able to select an item from list box 2, click on button 'Remove' and move the item back to list box 1 while it disappears from list box 2. How do I do this?