QuickBooks POS 19 project

I am looking to get a custom code to calculate total Quantity in the Group Inventory Field. Per Quick Books Point of Sale default it is set to zero and is not traced through/calculated through the system. We are selling both single piece products and grouped packs for wholesale buyers. We are trying to set webgility (ecommerce integration add on) to our online wholesale store but the group quantity set to zero does not let us run smooth inventory count available for purchase. The task is setting up a formula in one field in point of sale quickbooks. We need to be able to see available possible quantity of packs based on full available inventory of single products. There is an option in point of sale to build assembly which would deduct inventory from single items and combine it into assembly. Total numbers of assembly is displayed. However, it is not a feasible option is we want to sell in large quantities both single and grouped products. All the interested experienced candidates for Quickbooks POS are invited to apply and send their background details with this technology. Thanks in advance.