Dynamic Options - Data Linking Conundrum

I'm trying to create a very simple stock tracking system. I don't want to use any other eCommerce plugins as i'm doing this to create the steps of a system I can re use for other purposes.

The Idea:

I need to add an item to my stock list and register it on my daily summary (Form A) However the following day. I need to assign the stock previously registered the day before to a staff member within the same form, the following day.

Only IF the item is in stock.

I've put together a quick flowchart.

I'm looking for advice on the best way to go about this in terms of which formidable features could work best. I'm struggling to wrap my head around it. Custom coded suggestions would also be great if you think that's the most viable route?

Your feedback is appreciated

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