I have made a rough mock-up of the interface I believe would best meet the requirements we discussed yesterday. I hope it helps in your decision.

One page for each status:

• Page would contain a comment field and a checkbox to determine whether to re-use the comment or blank the comment field after an item is scanned.
• Each item scanned would appear with its history at the top of a list below the comment field and checkbox. Beside the comment for the current status would be a link that opens a field for editing the comment.
• Duplicate scans would be ignored.
• The database table would contain a barcode column and a time column and comment column for each status.

A history page would allow users to see the history for each item and to filter and sort by status and date. It would also allow users to see the history for a single item, and to search all comments or only those matching date and status criteria. The history page would allow administrators to delete entries.

I estimate two days to code and style the user interface, one day to code the barcode scanner interface, and up to two days for integration and testing with your site and equipment. So there's a possibility it only takes three days, in which case the cost would be US$900.