Is it possible for MS Excel to automatically insert a dash into scanned in numbers?

Let's say for example that I am scanning in barcodes with a scanner into an Excel workbook. These barcodes have numbers yet, if I want to replicate the dashes on the 'barcodes' (not isbn barcodes!) I need to enter those manually for each that I scan in. Is there a way in MS Excel (2003 professional ed.) that I can set it up so that after, say, every 6 digits a dash is inserted? Let me know if this needs more clarification and I'll edit this question.