sum by comparing 3 columns

Hello Anonymous 

Give this a try.

Measure = 
VAR _Blanks = CALCULATETABLE ( VALUES ( YourTable[Product] ), ALL ( YourTable ), ISBLANK ( YourTable[Weight] ) )
RETURN 
CALCULATE(
    SUM ( YourTable[Sales] ),
    KEEPFILTERS ( NOT YourTable[Product] IN ( _Blanks ) )
)

Anonymous 

This gives me the expected result on the sample data and correct totaling as well.  Give it a try:

Sum of Sales = 
SUMX (
    VALUES ( 'Table'[Product] ),
    CALCULATE (
        VAR _Blanks =
            CALCULATETABLE (
                FILTER (
                    ADDCOLUMNS (
                        CALCULATETABLE (
                            GROUPBY ( 'Table', 'Table'[Product], 'Table'[Sub Product] ),
                            'Table'[Category] <> "NA"
                        ),
                        "TheWeight", CALCULATE ( SUM ( 'Table'[Weight] ) )
                    ),
                    [TheWeight] = 0
                ),
                ALLEXCEPT ( 'Table', 'Table'[Product] ) )
        RETURN
            CALCULATE (
                SUM ( 'Table'[Sales] ),
                'Table'[Category] <> "NA",
                FILTER ( 'Table', COUNTROWS ( _Blanks ) = BLANK () ) ) ) )