How can we create MAPE Metrics out of Waterfall Analysis Output

Summary

How can we create MAPE Metrics out of Waterfall Analysis Output

Content

We are archiving the Demand Plan every week and generating new forecast.

Hence we are able to see the waterfall analysis for example measure-->Bookings Forecast 1 week ago. (Moving forward we will be able to see 2 weeks ago and 3 weeks ago as well)

Now based on these Waterfall analysis results, we want to build the MAPE Metrics by comparing Bookings History with Bookings Forecast 1 week ago. so that we can see the Weekly Accuracy in the Demand Plan. (Attached screenshot for reference)

I think seeded functionality does not show up MAPE Metrics for Weekly Waterfall analysis results.