Ok, let's try this again with more details.
We do inventory cycle counts once a week and to do so we scan the barcode of each article in the store using a barcode reader that feeds Excel via serial port interface. The data is entered in a specific column (I.e. column A) and every time a new article is entered it goes to the next row in the same column.
We have three categories of products as follows:
New
Used (u)
Defective (d)
When we scan the product ID of all items on the above categories, we need to find a a way to automatically add a specific character to the product ID to be scanned for each category. For example if we are going to scan the used articles, we would like to click in a button that automatically tells excel to capture the next product ID to be scanned with a leading "u" for used. Once the inventory count for used product is completed, the operator should turn off the button and then if more items are scanned then Excel keeps data without affecting the next product IDs.
A similar procedure should apply when the operator decides to scan the inventory of defective product but in this case the scanned items should include a leading "d".