Pivot Table Sum On Value Range

I have a data management issue that I have been able to resolve using SUMIFs and a custom table, but not in pivot form. Since the data source is a SQL database, I would prefer to resolve the issue in pivot form so that future values chart correctly. The data is formatted as so:

Job
Day Start
Day End
Size
Project

1
1/1/2014
1/10/2014
10
A

[Code] ......

From that data I want to see the total size of projects active at the start of the week for the past year. This would essentially mean summing the size of the projects if the week start date lies between the day start and end. This is what I ended up with:

Year
Month
Week
Weekday Start
Active Size

2014
1
1
1/1/14
10

[Code] .....

This is the associated pivot chart:

This would be "OK" except that I would also like to see the size breakdown by project, like this:

This is where I would need the data to be handled purely in a pivot so that when a new project is added, the pivot table will automatically make the summing column for it rather than my manual creation of columns for the data.

I have uploaded a link to a work book with the examples of the data and how I made the charts above. You can see that to make the second chart I had to manually create the columns for each project:

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