This guide works well for people who have fixed number of items in their store. I usually sell the same items, but I needed a way to to update the quantity of those without having to click on each individual item.

• Start from the My Ebay page. 
• Under Selling Manager Pro, Click on Active Items.
• On the Active Items page you can either click on the box next to the word Title (It will put a check in all of the boxes on the page) or you can just check the boxes next to the items you want to update.
• Next, Click on the Edit button, which is located next to the Search button on the right side of the page (bottom or top of page).
• OK, now here is the important part. At the top of the page under Select Listing Information, there is a box labeled Quantity. Check this box and any other box that you may want to update.
• At the bottom of the page under Select Edit Method Click Edit listings Individually.
• Click the Continue button at the bottom of the page. You will go to a page that will verify your listings. This may take a few minute to complete.
• When this is complete you will have all of your listings on one page with the Quantity box visible so you can update.

It may be easier to add an item number to the title on your listing so you can find if faster and update. I have found this to be a quick way to update all of my listings (currently 100) without having to click on each individual item.

-Scott