You'd use the same basic set up for scanning in either case, you'd just scan into a different field and trigger a different script at the end of the scan to look up the gift card record instead of looking up an inventory item.
You can program barcode scanners to append special characters to the beginning and end of the scanned info. You can set up OnKeystroke script triggers to respond to these characters to place the cursor in the right field to recieve the scan and then to trigger a script when the scanned data has been entered.
If your gift card codes are distinct from your inventory codes, you could even create a script that does handles both types of scan events.
Note: mag stripe readers can read the magnetic strips off gift cards with mag stripes in pretty much the same fashion.
Thank you for this information. I am still unsure as to how we could hook up filemaker to subtract a redemption amount from the original amount on the gift card as we cannot change the barcodes when someone comes into the store to buy something...
You'd need a table of gift card records with at least the current balance and the barcode.
You would complete the invoice so that the amount due is computed then scan the giftcard.
Your script would use the scanned bar code to look up their balance, logging a payment to the invoice and deducting the payment from the current balance.
There are a number of different variations possible depending on how detailed a record you want to keep. (You could log each use of the gift card in a check register type ledger and use summary fields to compute the current balance) and how many options you want to offer your customers. Can they put more cash on the card at a later date?, Can they pay for an invoice by taking $10 from the card and using a different payment source for the rest?
All those options and more can be implemented if you design your database and scripts to support them.