Sum latest values, but not over years

[Bschwalb]

We have an issue that I'm not sure we can solve:

We have one value per building per month.

This is the current value at the time, so each building should show the latest value.

The buildings are collected into groups - these should show the sum of all buildings (latest value each).

However, I can't get it to work.

Here's what I have so far:

Sum(Aggr(FirstSortedValue([Value], -[enddate]), [Building], Year))

This leads to the result as shown above. The years are right, but the building is a SUM of the years, but it should be only the latest.

If I leave out the "Year" in the Aggr-function, the sum is right, but I only get one value per building, not one per year per building (when drilling down).

What I need is a function which returns:

The sum of the latest value value per building for all buildings in a group (with varying hierarchies), per year in this visualization. 

I hope that makes sense, maybe someone more experienced knows of a solution to this.