FX Variance calculation - SUMX doesn't work

Hi all,

I need to conduct variance analysis on some financials including the impact of changes in fx rates.  The variance calculation is:

Actual Revenue_Base Currency - (Actual Revenue_Local Currency / Budget Fx Rate)

This is fine when there is only 2 currencies, however, in my data there is 10 different currencies and as a result the above calculation needs to be done at an individual row level and then 'summed up'.  To do this, I used SUMX e.g.

SUMX(Table, Actual Revenue_Base Currency) - (SUMX(Table, Actual Revenue_Local Currency) / (SUMX(Table, Budget Revenue_Local Currency)/SUMX(Table, Budget Revenue_Base Currency))

Results are correct at an individual currency level, however, the total is completey wrong as it appears that for the grand total is recalculating the variance as opposed to 'summing up' the individual parts.  A simple example is below, would appreciate any help.  Thanks,

Dan