Primavera Data Source - Pivoting Date Columns

Afternoon Everyone.

I was wondering if someone can help me.  At present P6 in the company I work for is not directly connected to PowerBi.  

I want to create a planning dashboard using data from P6.  I have set up a report in P6 which downloads it to an excel file which I point to PowerBi.

As an example below I have several columns which contain information, and then to the right date columns. These date column headers will change as and when the schedule changes.

Previously I use to 

1. Promote Headers 
2. Then Pivot selected columns from the first date to the end date

However, the issue is if the date changes (which it does, or additional dates are added) the re-fresh throws up an error.

Someone previoiusly told me to pivot the date columns first then promote the headers, but this doesn't appear to work and pull in the data?