Store Checkout: (product data change) Can't Find Where and How Help?

Any advice will be greatly appreciated. Looking for the correct way.

I am on the very last 2 issues on my 2nd app (hopefully) and cannot for the life of me figure out where or how this can be done. Probably way overthinking it.

To start, I used the free template Marketplace. Everything works great.

I figured out how it is usually done, and/or I could easily do it manually. I just think because how we do business here, the normal way could become a huge mess.

The situation: We have items for sale where the quantity is one. and because we get paid mostly by wire, company check, and some when its delivered. Which could take a week if not more, I don’t want to take it out of inventory (for sale) when they add the item to their cart.

I want to change the item from for sale to pending sale. BUT only after they click order submit on my checkout page.

My concern is, I don’t want to give a user the ability to add everything to their cart, and it is now not for sale and they havent even submitted the order.

BIG ISSUE: When the user hits submit order on this page, I need to change that one list of things on the individual items database…

I have the list of things set up, and how that changes on the actual product page. Got all that.

But as this groups element data source is parent groups user… I cannot seem to figure out how I can change the after submit now to the parent groups product.

Also I am thinking usually this data is changed in some sort of transactions or orders data, but for the life of me I cannot figure out how to find that and change it.

Any advice, thanks.