@Lynda
One way of accomplishing your task is by using the ItemInventory table with the QuantityOnHand field from QB. You can create a drop-down menu in Method, that contains an "on hand" field that will reflects the QuantityOnHand amount. So when your sales representative are searching for the inventory item from the drop-down list, it will show the item's name and the respective quantity amount.
Please let me know if you require any further assistance