Is there a way to only take a transaction fee on some stores but not all?

I was wondering if there was a way to only take a transaction fee for some stores but not for all stores. I am looking for ways to get more people to open stores and was thinking of offering a “no-transaction fees for a year if you open a store by Sept. 30” campaign. Is there a way to set up those stores to not have a transaction fee but stores who open later to have one? I have attempted to change a few stores to Paypal Express verses chained payments, but then I would need API information and stuff I think most of my store owners wouldn’t be able to figure out. It was hard enough to get them to this point…just wondering if there is another way like maybe through the blog template or something…