Calculate next highest Part in same Case by Amount

Hello _96bp,

Can you please try this DAX approach:

TopRelatedMaterial = 
VAR SelectedMNr = SELECTEDVALUE(MP[MNr]) -- Assuming there's a way to select a single MNr, like a slicer.
VAR RelatedMaterials = 
    CALCULATETABLE(
        SUMMARIZE(MP, MP[ID], MP[MNr], "TotalAmount", SUM(MP[Amount])),
        NOT(ISBLANK(MP[Amount])),
        MP[MNr] <> SelectedMNr
    )
VAR SharedCasesWithSelectedMNr = 
    CALCULATETABLE(
        DISTINCT(MP[ID]),
        MP[MNr] = SelectedMNr
    )
VAR FilteredRelatedMaterials = 
    FILTER(
        RelatedMaterials,
        MP[ID] IN SharedCasesWithSelectedMNr
    )
VAR SummarizedRelatedMaterials = 
    SUMMARIZE(
        FilteredRelatedMaterials,
        MP[MNr],
        "SumAmount", SUMX(FILTEREDRelatedMaterials, [TotalAmount])
    )
VAR RankedMaterials = 
    ADDCOLUMNS(
        SummarizedRelatedMaterials,
        "Rank", RANKX(SummarizedRelatedMaterials, [SumAmount],, DESC, Dense)
    )
RETURN
    MAXX(FILTER(RankedMaterials, [Rank] = 1), MP[MNr])