I was looking at how this might be done, but the subcategory (product list) page is currently implemented from a Template file that loads a module into a ListView control. So as I see it the "Add All to Cart" button would have to go on the Template file and somehow reference all the items displayed in the module (ex ProductBox1) within the ListView control. Is that an easy thing to implement?
Of course, there would have to be a numeric text box to capture the quantity of each item or a checkbox on each listed product to indicate which products to select. That part I understand. It's how the Template file would know to reference each product listed in order to submit all to the cart that I can't figure out. Any ideas?