Grouped summaries with conditional filtering

Anonymous - If the answers you have given me are true and all your data lives in the CBAM_Goods_InScope table then the DAX for a Dynamic measure I gave you earlier works. I have copied it below again:

VAR Threshold = [SelectedThreshold]

VAR HighValueEntries =
    CALCULATETABLE (
        VALUES ( 'CBAM_Goods_InScope'[EntryIdentifier] ),
        FILTER (
            ADDCOLUMNS (
                VALUES ( 'CBAM_Goods_InScope'[EntryIdentifier] ),
                "@CustomsValue", CALCULATE ( SUM ( 'CBAM_Goods_InScope'[CustomsValue] ) )
            ),
            [@CustomsValue] > Threshold
        )
    )

RETURN
    CALCULATE (
        SUM ( 'CBAM_Goods_InScope'[SupplementaryUnitQty] ),
        KEEPFILTERS ( 'CBAM_Goods_InScope'[EntryIdentifier] IN HighValueEntries )
    )

I will repeat, you cannot do this dynamically within a physical DAX calculated table, because they do not re-calculate every time a parameter changes, a.k.a they are static. 

If you want this to be dynamic, then you will have to use a measure. Use the DAX I have given you above. It creates a virtual table, based on the selectedThreshold, and the SupplementaryUnitQty is then calculated over this table. It is the most optimal and performance efficient version of this calculation you will get. 

I am attaching my file so you can investigate it working, and below are some screenshots to show it dynamically calculating based on the value in the slicer. 

If I answered your question please mark my post as the solution, it helps others with the same challenge find the answer!