Weighted average rate for total

[Anonymous]

Hi!

I am working on revaluating outstanding balances on a specific date at the exchange rate in the system for that date.

As it happens that 2 or more values for a currency's exchange rates get captured in the system on a given date, I pick up the relevant exchange rate via the following measure:
Exchange rate at selected date = MAXX(TOPN(1;FILTER('Exchange Rate';'Exchange Rate'[exchange_date]<=[SelectedDate]);'Exchange Rate'[exchange_date];DESC);'Exchange Rate'[exchange_rate])

This works fine for my purposes, BUT on the total line it pulls up the max of all the exchange rates whilst I would rather show the weighted average.

The big problem comes in when calculating the total revaluation amount. Per currency it works fine, but instead of adding the total in the total line it calculates the total as Total Balance in Invoiced currency x Max of all exchange rates.

The correct answer in the total line for the revaluation amount should be either
1) sum of all the revaluation amounts calculated    or else
2) Total balance in Invoiced currency x weighted average exchange rate



Please help!