Calculating Date Difference on condition

Hello meghansh 
To achieve the desired result, you can utilize the following DAX formula:

Difference = 
VAR _id = PhaseTbl[ID]
VAR _phaseNum = PhaseTbl[PhaseSequence]
VAR _conditionalPhaseNum = IF(PhaseTbl[HasPhase2] = "No", 1, _phaseNum-1)
VAR _deductionAmount = 
CALCULATE(
    SUM(PhaseTbl[Amount]),
    FILTER(
        ALL(PhaseTbl),
        PhaseTbl[ID] = _id && PhaseTbl[PhaseSequence] = _conditionalPhaseNum
))

RETURN
IF(PhaseTbl[PhaseSequence] <> 1, PhaseTbl[Amount] -_deductionAmount)

Here is the screenshot of the solution for your reference:

Best Regards,
Udit

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Hi meghansh 

It seems that you want to calculate the difference row by row for different IDs. Besides the method provided by quantumudit , you can also consider the following method.

First create an index column in power query:

Then you can try the following measure:

Measure = 
var _ID = SELECTEDVALUE('Table'[ID])
VAR _index = SELECTEDVALUE('Table'[Index])
var _current = SELECTEDVALUE('Table'[Amount])
VAR _previous = CALCULATE(SELECTEDVALUE('Table'[Amount]),FILTER(ALL('Table'),'Table'[Index] = _index -1 && 'Table'[ID] = _ID))

RETURN
IF(_previous <> BLANK(),_current - _previous,BLANK())

Select "show items with no data"

Result:

Best Regards,

Jayleny

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