Reporting tool based on a handfull of variables

We need to have a tool to monitor the number of visitors to our fitness centers (currently two but more will be added). Visitors can be 1) members, 2) multiport visits, 3) classes in currently two centers. Later on the number of centers will increase. Manually the figures are the three categories are entered and the accumulate will appear automatically. Further more variables such as cancellations/frozen memberships are entered manually on a monthly basis. Once figures are entered the program shall calculate the accumulate number of visits by month and in total. We have worked with a simple file. We know it can be done much smarter. SHow us your offer. We would expect further alteration later on, so it needs to be flexible and adoptable to new changes later on. Preferably, we shall be able to do those changes ourselves. Only if larger projects we may reach out for more programming needs.