Form to quickly edit single column based on input of row key

[BombusT]

I'm guessing this is rather simple but have been floundering so would appreciate some guidance.

I want a simple form where the user can input the key value of a table and the form finds that row and automatically updates a column with today's date. Pretty much as simple as that. I don't want the user to have to manual add the date to a column or interact with it otherwise, they will be using a barcode scanner to input the key and I would have the form loop back with auto re-open.

I thought this might be the purpose of the "Row key" option in form view type but using =input("Barcode", "") it keeps telling me that there is already a row with that key, so clearly is behaving differently from what I expected. I've noted that if I set the "Row key" value to a specific key value in the table and have an action set to update the column field when the form saves, it works perfectly. So how do I dynamically input that "Row key" value?

I managed to get something working where I had a separate table that recorded my changes and a bot that updated the main table, however since it is a large database I would rather avoid adding an additional table and rows. There would be thousands of scans per week and it would quickly add up.

Edit: I have also done this with a second "dummy" table with grouped actions that update the main table then deletes the row from the "dummy" table (to minimise database size), but surely there is a way to do this with fewer steps?