Below image is what I create for my "Order" table.
The Item field is related to my inventory table. Currently, I use pop-up menu for the item field and its value is from "Inventory" table's primary ID but display using second field. However, in this case, every time when I need to create an order invoice I need to select the item from the pop-up menu list one by one. Is there a convenient way that I could key-in the item name directly from field but it will still pull related information, such as its price.