Calculator

I need help building a calculator similar to the example here: [login to view URL] The needed calculator will look similar but the functions will differ a bit. The user will input the amount of their purchase, how many months or weeks to pay for the product and the payment start date. With this information the calculator should produce the user's payment amount on a monthly, bi-weekly or weekly basis. The user will input the amount of their purchase and the calculator will simply divide that payment into 6 monthly payments, 12 bi-weekly payments or 24 weekly payments. For example: The user inputs a product cost amount of $985 the calculator should post a monthly payment of $164.17. or $82.08 for bi-weekly payments.