Cumulated key figure - formula

Hi,

We have a requirement of calculating YTD Actual % for each month

Reports columns

Current Years Cumulative Sale

Previous years Cumulative Sales

YTD Actual %

Formula: (((Current Years Cumulative Sale / Previous years Cumulative Sales) -1 ) * 100)

Report rows are from Jan to Dec.

YTD Actual is calculating % for each row (Sale for current and prior year) instead of summing up all previous rows sales (cum sale).

Any one knows any solution to this?

Steve