Set Analysis for Latest day of the Week sales divides by Prior 8 weeks total sales

[munibridgei2i]

Hi ,

Could any one please help me  how to write an set expression for the below requirement or please suggest me how to proceed.

Numerator/Denominatory: sum of sales for Latest day in a week / sum of Prior 8 weeks total sales but not the same week

Thanks in Advance.

Krishna