Most of our orders are temperature sensitive so ship Monday-Wednesday to avoid weekend delays. Many of my customers place multiple orders over the weekend before their shipment departs. I want to encourage them to continue adding on items to their order by offering a reduced shipping cost for additional orders. Is there any way for my system or an app to query if they have an order pending shipment so that it will charge less on shipping when they check-out? I have offered the add-on option at checkout with very specific instructions in the description (that the customer needed to have a pending order to qualify). However, I found that many customers would select the add-on even if they had no previous orders. Alternatively, I've tried sending customers a discount code for free shipping with their order confirmation. However, some of them have misused the code by sharing with friends or applied it to an order weeks later after their original order had been sent out. I've thought about offering free shipping or flat rate shipping on all orders and building the price of shipping into the cost of our products. However, if I do this our listed prices are less competitive with other vendors.