Automatic Fee Calculator in php

We need an automatic fee calculator for our website. It should get integrated in our webpage (php) and we should be able to modify it at the back end i.e. we should be able to change applicable the fee, add new programs etc. The student should be able to select his/her country, select the mode of learning (online or full time), select the program applying for from the dropdown list, and the fee should get automatically calculated. After the fee gets calculated the student should be able to click on a button such as 'pay now' which should take him to our paypal payment page and paypal should charge the amount calculated by the payment calculator.