Reset cummulative total/running total when other column value is TRUE

[justlogmein]

What I want to do is pretty straightforward but all the examples I have tried have not worked so far and I'm stressing a little because I need to complete this today.

I have a table of engine oil samples for heavy mining machinery and a column called "Engine Oil Changed" which indicates if the engine oil was changed when that sample was taken. Now I simply want to find out how many hours the oil had before it was changed. I have a running total column for the hours which works fine. I just need to reset this running total when the "Engine Oil Changed" column is true, noting that I need to have it grouped by "Unit Number".

Is anyone able to provide some code to put into this column?

https://jmservicescomau-my.sharepoint.com/:u:/g/personal/jacob_jmservices_com_au/EaFFuIzsncpKiGoUSuw...

[tamerj1]

@justlogmein 
Hope it's not too late 🙂

Here is the sample file with the solution https://www.dropbox.com/t/HZEL59KsSFlicaPV 
Please use the following code

Fluid Hours Reset when Oil Changed = 
IF ( 
    'Sample Data'[Oil Changed] = FALSE ( ),
    VAR CurrentDate = 'Sample Data'[Sample Date]
    VAR DatesBeforeTable1 = FILTER ( 'Sample Data', 'Sample Data'[Sample Date] <= CurrentDate )
    VAR DatesBeforeTable2 = FILTER ( 'Sample Data', 'Sample Data'[Sample Date] < CurrentDate )
    VAR PrevuiousChangesTable = FILTER ( DatesBeforeTable2, 'Sample Data'[Oil Changed] = TRUE ( ) )
    VAR PreviousChangeDate = MAXX ( PrevuiousChangesTable, 'Sample Data'[Sample Date] )
    VAR ResultTable = FILTER ( DatesBeforeTable1, 'Sample Data'[Sample Date] > PreviousChangeDate )
    RETURN
        SUMX (
            ResultTable,
            'Sample Data'[Hours Since Previous Reading]
        )
)

 If you want to include the last change hours with the sum use this code with a very tiny change

Fluid Hours Reset when Oil Changed = 
IF ( 
    'Sample Data'[Oil Changed] = FALSE ( ),
    VAR CurrentDate = 'Sample Data'[Sample Date]
    VAR DatesBeforeTable1 = FILTER ( 'Sample Data', 'Sample Data'[Sample Date] <= CurrentDate )
    VAR DatesBeforeTable2 = FILTER ( 'Sample Data', 'Sample Data'[Sample Date] < CurrentDate )
    VAR PrevuiousChangesTable = FILTER ( DatesBeforeTable2, 'Sample Data'[Oil Changed] = TRUE ( ) )
    VAR PreviousChangeDate = MAXX ( PrevuiousChangesTable, 'Sample Data'[Sample Date] )
    VAR ResultTable = FILTER ( DatesBeforeTable1, 'Sample Data'[Sample Date] >= PreviousChangeDate )
    RETURN
        SUMX (
            ResultTable,
            'Sample Data'[Hours Since Previous Reading]
        )
)