NETWORKDAYS between two tables containing duplicate OrderIDs

Hi, Fredde86 
Based on your information, I created sample tables:

Then create a new measure, try the following DAX expression:

Diff Days *History* = 
    SUMX (
        FILTER (
            MANUFACTURING_ORDERS_HISTORY,
            MANUFACTURING_ORDERS_HISTORY[OrderID] = MAX(ITEM_TRANSACTION_HISTORY_SUM[OrderID]) &&
            MANUFACTURING_ORDERS_HISTORY[Item Nr] = MAX(ITEM_TRANSACTION_HISTORY_SUM[Item Nr])
        ),
        NETWORKDAYS (
            MANUFACTURING_ORDERS_HISTORY[Due Date History],
            MAX(ITEM_TRANSACTION_HISTORY_SUM[Date])
        )
    )

Put it in table visual, here is my preview:

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Best Regards

Yongkang Hua

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