we had a CSG mod for something similar, it was a child table on the lot table, the company was a stockholder, so had to have traceability for individual bars.
Each delivery was given its own lot number and then each bar was given a number under that, for example, Lot 4500, would have bars 4500/1, 4500/2 etc
The length of each bar was recorded. as well as any treatments that happened to it. It was a massively intrusive mod, but required, each bar was labelled and could be picked at any issuing, reserving or allocating screen.
When the bar had been cut, the length was updated and returned to stock.