Conditional Summing based on the last time one value occured

Hi, since I want to calculate the process time after the Maximum Index of each conditions (or remarks) i think the condition for the index should be > max index not <= max index. Fix this code but now it will return 0 value. 

So if input < in the formula, it will calculate all process time, and if I input > in the formula it will not calculate any process time 

the revised code is 

Time = 
CALCULATE (
    SUMX ( DATA, DATA[Duration (Hour)] ),
    DATA[Remarks] = "Process Time",
    FILTER ( ALLSELECTED(DATA), DATA[Index] > [Maximum index] )
)

I suspect that the maximum index in that code is refer to the process time itself since it also has index number. So when I choose < it will calculate all the process time since all process time will have index <= maximum index of process time and when I choose > it will calculate no process time since no process time will have index greater than the maximum index of the table itself.  I hope it is clear.

So basically I need a function to specifiy the max index for each unique column not max index of the table or the process time.

Below is some snapshot.

Any help will be appreciated.

Regards,

Handy Pratama