Pivot Table custom formula

Hi!

I have two questions regarding pivot tables:

#1 - when inserting a custom formula in a pivot table, eg. divide field A with field B, what the pivot table does is to sum all records of A and divide it with the sum of all records of B. I'm assuming this is correct.

The question is: what if I want to divide the first record of A with the first of B, the second record of A with the second record of B, all the way to the nth record and then FINALLY, sum up the result?

I hope I was clear.

#2 - is it possible to multiply a pivot table total with another number? I tried to create a new formula but Excel tells me it isn't possible. Can I bypass this problem?

Thank you in advance!