How do I add a button that lets customers buy multiple products in my Product Groups?

When you create a product group using Product-Group Display Format 2, the Multi-Buy button, which allows a customer to add multiple products to his or her cart from one click, behaves as follows:

• If all of the products in the group do not have product options nor product personalization questions, a Multi-Buy button is displayed at the bottom allowing the customer to add multiple items to cart (i.e. The Multi-Buy button is not available if even one of the products assigned to the respective Product Group has product options or product personalization).
• If the Qty field is left blank, that product is not added.
• The Multi-Buy button is a different image than the standard buy.gif button and can be replaced though FTP. The image name of the Multi-Buy button is: “buy_group.gif”.

Limitation: If one of the sub items has product options or product personalization questions, the multi-add button won't be displayed.