I am using the membership plugin for memberships that we offer at my office building. I was wondering if the payment portion of the membership plugin can be edited to include additional services. for example, we change a monthly fee as well as a one time $60 administrator fee for signing up. Right now with the plugin, the only thing I can charge for is the monthly recurring fee and not the $60 administrator fee. I want the system to be able to add the fee to the shopping cart when they check out.