Cannot sort by measure based on another measure

Anonymous

Assume I have table called InvoiceDetail, which contain column:

SpendInEUR

SpendInGBP

SpendInUSD

SavingsInEUR

SavingsInGBP

SavingsInUSD

So on the Power BI, we allow user chooses which currency they want to show using ChicletSlicer like that:

And then we calculate measure Spend and Savings based on which currency is opted

Spend = 
IF (
    LASTNONBLANK ( 'DefaultCurrency'[Code], 1 ) = "GBP",
    SUM ( InvoiceDetail[SpendInGBP]),
    IF (
        LASTNONBLANK ( DefaultCurrency[Code], 1 ) = "USD",
        SUM ( InvoiceDetail[SpendInUSD] ),
        SUM ( InvoiceDetail[SpendInEUR] )
    )
) 

Savings = 
IF (
    LASTNONBLANK ( 'DefaultCurrency'[Code], 1 ) = "GBP",
    SUM ( InvoiceDetail[SavingsInGBP]),
    IF (
        LASTNONBLANK ( DefaultCurrency[Code], 1 ) = "USD",
        SUM ( InvoiceDetail[SavingsInUSD] ),
        SUM ( InvoiceDetail[SavingsInEUR] )
    )
)

Thanks for your help