How to Show Contiguous Sum Trend Based on Timestamped Value Table

Hi, Anonymous 

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Table:

Calendar(a calculated table):

Calendar = CALENDARAUTO()

There is no relationship between two tables. You may create a measure as below.

Result = 
var tab = 
ADDCOLUMNS(
    SUMMARIZE(
        FILTER(
            ALL('Table'),
            'Table'[Update Date]<=SELECTEDVALUE('Calendar'[Date])
        ),
        'Table'[Product Name],
        'Table'[Part Number],
        "MaxDate",MAX('Table'[Update Date])
    ),
    "Cost",
    CALCULATE(
        SUM('Table'[Part Cost]),
        FILTER(
            ALL('Table'),
            'Table'[Product Name]=EARLIER('Table'[Product Name])&&
            'Table'[Part Number]=EARLIER('Table'[Part Number])&&
            'Table'[Update Date]=EARLIER([MaxDate])
        )
    )
)
return
SUMX(
    FILTER(
        tab,
        [Product Name]=SELECTEDVALUE('Table'[Product Name])
    ),
    [Cost]
)

Result:

Best Regards

Allan

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.