Calculate average maturity on customer basis (sales dependent)

[selimkocak]

Hello there,

I would like to take the average grade of customer-based futures sales bills as in the case of excel in the trade.

Thanks in advance for your help

sample

customer ID    date    maturity    sales

20434307    6.01.2017    5.07.2017    115

20434307    6.01.2017    8.01.2017    339

(maturity * sales / total(sales) ) ,custumerID

stalwar1‌

[OmarBenSalem]

What is the supposed right result for this 2 lines?

Maybe?