Calculated coulumn - value diffrence, betweek last and earlier value

[MGorak]

Hello

I,m try to make calculated coulumn with value diffrence, actual and last(in SPC, diffrence between measure and last measure).

But only in this same Product code and Measure number (Atrybut coulumn, M1,M2....)

This calulumn not work propperly

Thank You

Diffrence =

VAR a =

    CALCULATE (

        FIRSTNONBLANK ( 'Counterlid Claudia 609 StartREC spc'[Value],  0),

        FILTER ( 'Counterlid Claudia 609 StartREC spc', 'Counterlid Claudia 609 StartREC spc'[StartDateTime] = EARLIER ( 'Counterlid Claudia 609 StartREC spc'[StartDateTime] ) )

    )

RETURN

    IF ( a = BLANK (), 0, ABS (  'Counterlid Claudia 609 StartREC spc'[Value] ) - a )

[tamerj1]

Hi @MGorak 
What is the expected result? Also please clarify which one is considered the last value?

[MGorak]

Expected is diffrenece between last two mesaurments like below

Last by Date/Time in coulumn StartDataTime

[tamerj1]

@MGorak 

In order to understand exactly what is you intended result, kindly provide the correct values in the screenshot below. Thank you.

[MGorak]