Show total weight when bulk-selecting orders for a purchase order

We order gray granite by the truckload and cut the order at about 26,000 lbs, sometimes 28,000 to 30,000 depending on how much import stone is coming in. When I select orders in bulk to make a purchase order, I need to see the total weight of what I have selected, not the order value.

Right now nothing adds the weight up, so I track the load on a separate spreadsheet. A running total, ideally with a flag when I reach my truckload limit, would let me build the whole load into one PO.