Insert Function for SmartWarehouse

[Frank Simanapang]

Hello there,,
i wanna make some project, make SmartWH using RFID + VB6 + MySQL.
ok what i want to do is, when somebody take some item on shelf, it will goin through tag-reader and recorded to DB as 'on hand' and after that item pass to end gate (another tag-reader), it would be set on DB as 'cash out', because sometimes they might be canceled to pick the item through the end gate for some reason (out of cash, change their mind, etc). so what is the solution of that algorithm?

open for any solution, suggest or even criticism.
Thnx Beforehand.