CGPA Calculator in PHP

Good day every one
I am on a final year school project for Bsc Computer Science and my project is a cgpa calculator. I actually thought it was going to be an easy ride but am damn wrong.
The project is meant to to calculate your GP (the usual university way of calculating CGPA) and grade the student(s) accordingly(first class, 2.1, 2.2 etc). The following are the steps

Front End Page

  1. A login form asking for the student record (e.g username and password)
  2. A page where he selects the courses he took with respect to the year
  3. A page that displays the total computation and the grade (CGPA) of the student
  4. A Page asking to either print the result or mail it to the designated address.

Back End Page

  1. Administrative login
  2. A Page to input the courses, the course code, their respective unit, and whether it is compulsory or elective
  3. A page to upload the user details

There is really no issue with the login form that has been resolved, the issue is the mathematical computation for the courses in order to do the calculation and taking into considerations that some people will definitely have carry overs (this is really the headache that I have)

Please fellows, I need help so that this almighty University can let me go.

Thank you guys as I await your response

Ok… Could you please post more information, like an outline or project description.