Basic Windows/Mac compatible software needed

I am needing to create a program that has a version for both Windows and Mac users. It seems to be relatively simple. It needs to be a start up application, so that it pops up with an open window when the computer starts up. The application itself consists of: - Daily questions - Weekly questions - Monthly questions That means when the application opens, it will display the daily questions every day, the weekly questions once a week (plus the daily questions), and the monthly questions once a month (plus the daily questions). There are about 20 questions. The user will answer the questions in a large text field underneath each question. (20 questions, 20 text fields.) When completed, the user has to be able to save the answers. They can be saved in a local database, xml file, or whatever. Ideally something that won't take up too much space over the course of a year or two. There should also be some basic form validation so that each question needs some sort of answer, or else a check box that says "n/a" to skip that question. If n/a is checked, then that question does not need to be answered. If possible, I need this project completed within the next 2 weeks.