Nearly every shopping cart I use as a BUYER has the feature that if I've already added an item to my shopping cart and I try to add it again - it gives me a warning something like "This item is already in your cart - if you want to change the quantity view your shopping cart and update it there".

In the last few days I've had a few customers accidentally add TWO of the same cross stitch books to their carts. This also occurs when my customers purchase thread because they are ofen buying 100 or more thread colors and it's hard to see on the cart if they have purchased them or not.

Is there a way to change my settings so the customer MUST use the quantity update on their cart ONCE the item as already been added? Of course they could initially add as many as they want using the QTY on the product listing.