Barcode cards

I haven't talked about my Zumba classes lately. They are still going strong. Actually, I'm adding a Hip Hop Hustle class to the lineup this week. I'm very excited about it. Now that I'll be teaching 4 classes a week, I've been thinking about adding an 'unlimited' monthly pass for my attendees. I'm just not sure how to work it. In my ideal world (which is not always the real world), I'd get some plastic cards that I could print barcodes on and scan them at the registration desk. Then I can keep track of how often the passes are being used. I'm pretty sure that is super expensive though. (See, this is why I need a sugar daddy!) If anyone out there has any experience with barcode readers and whatnot, please let me know. I'd really like to have something like that but I don't have a ton of money to spend on it.