Many spreadsheet applications nowadays have functionality above and beyond the traditional, offering a variety of charts, look-up tables, databases and more functionality than can be mentioned here.
Rather than having to go through the pain and suffering of learning a new technology and having to experience trial and error development, the best route would be to acquire the services of a consultant, who can identify your needs and create a customised solution. Obviously, the cost of such a project would depend on the size and complexity of the spreadsheet and your requirements. However, you might be surprised at how cost-effective this project would be.
These are the pros and cons of selling spreadsheets. The real beauty in this idea is that you could do the work once and there is no limit to how much you can earn, especially with effective use of the internet and other mass communication tools.
Once you design the type of budgeting spreadsheets you want to use, it will be easy to copy it for subsequent months or years. You can also use just one sheet and create tabs for each month.