Need help!! Create percentage inside each class

Hi everybody!
I m writing from Italy and I am not able to go out from a vba problEM
As you can see in the attached file, I have a column of classes , a columns of related revenues and the total for eache class.
I have to create a column, next to these, where I can create the percentage with respect the sum of each class (as you can see by the formula).
My problem is I am not able to say vba to find the totals and to create the percentage just with the revenues related to that total.
Thanks in advance for the help, I really need them.
I cannot understand how to create this.
Thank everybody!!
Max
p.s: I have to work on excel2010

Hi Arkadi!!
First of all, thank you for the reply!!
I try to explain better cause in my previus post I have been not so clear
tha table represents output of pivot.
The column B are some classes (the percentage in the name of the classes maybe are ambigous, just call them class A,B,C,D,E,F,G,H). For each class, IF there are elements in the database of the pivot, there are the sum of the revenues.
So, for example, for a product X, there are maybe class, A,C,F,H and the related revenues. at the end of product X there is the sum.
for another product, let s say Y, there are just A,G,H classes with the related revenues and sums.
And so on.
With another extraction from pivot, I could have product with all the classes, or just 3, or 4, ..... . That 's the problem. Every products could have different number of classes (and so rows).
What I need is a column, after the revenues, where there aren't the absolute values of the revenues, but the percentage with respect to the specific sum.
I need to say to vba to find each sum related to the product and create the percentage.
I tried the code you kindly wrote but it doesnt create the right percentage.
Now I am trying to find a solution (but not sure no be able).
I attached a better version of excel file.
Thanks!!!!

Hi Arkadi!!
Yes you are right!!
the cell next to total in column B si always blank.And pivot already gives me that total.
I just have to create two colomuns next to pivot with the percentages of the "weight" of each class, with respctc to the total of each category.
But the pivot extractions can vary a lot. Sometimes a category with all the classes can be followed by another with just one class (and so the class and the total have the same value. ), and then another with 3 classes and so on. Thanks for your help.
Massimo

Hi Arkadi!!!
This code works so well!!! I understand how my knowledge in vba is full of gaps!!
When the interval are fixed I can write right codes , but , as in this case when they vary, I am unprepared.
The last thing. In the percentage columns create by the code, the cells corresponding to the total are blank. Obviusly that cells always are 100%.
Would it be possible to calculate even this cell, in order to make appears the value 100% ?
I'm trying to modify your code to do this, but unsuccefully...
Still thanks for this great help
Massimo

It works perfectly!!!
Thanks a lot!!!!!
Massimo