product type: hotel room voucher (ticket to stay at hotel for a night)
every voucher is unique and have a unique serial number
How to design my order form to avoid my sales team entering already sold voucher serial number? (In practice they may occur multiple ongoing order selling same type of voucher with same serial number)
How to design my order form to let my sales team only entering how many voucher they are selling (of each type of voucher) and the form automatically fill in the latest un-sold serial number?