Demantra Series Creation

Hi All

I am a Junior Consultant in Demantra with just 3 months experience in it and I am tasked with creating a series that will be saved as a level attribute.

I am working in a business that wants to create a series called "Item Returns Percentage" they need it to be populated once off with a percentage value that will be used in a calculation to determine a Final Forecast. The calculation should have look something like this (I am not going to put it in the Demantra format this is just how the calculation should look)

Returns will be loaded via a CSV File.