Yes you can! The items must be in your Inventory page in order to do this. Go to manage under the listings tab, and select all the items you would like to mark (or Select All). Once you have selected the items, scroll down and click "Sold Outside of POP."  This will take you to a page you can enter the information for all of the items selected.  Only the "Name" box is required. Be sure to click Submit to complete the sale.