I have create a student rank.dbf with five fields namely 1. English 2. Maths 3. Science 4. Total marks 5. Rank.

I want to put the Rank for each student based on their Total marks secured.The total marks is out of 500.


For example student A secured total marks is 489 out of 500 and student B is 492 and student C is 389 and student D is 391.

The Rank for Student B is 1 and student A is 2 and student D is 3 and student C is 4.

How to Write source code?