Combine particular column values from above rows

k_mathana - See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586.
The basic pattern is:
Column = 
  VAR __Current = [Value]
  VAR __Previous = MAXX(FILTER('Table','Table'[Date] < EARLIER('Table'[Date])),[Value])
RETURN
  __Current - __Previous

In your case, something along the lines of:

Cumulated Text = 
    VAR __Table1 = SELECTCOLUMNS(FILTER(FILTER('Table (8)',[Date]<=EARLIER([Date])),[Text]<>BLANK() && LEFT([Text],1)<>"X"),"Text",[Text])
    VAR __Table2 = SELECTCOLUMNS(ADDCOLUMNS(SELECTCOLUMNS(FILTER(FILTER('Table (8)',[Date]<=EARLIER([Date])),[Text]<>BLANK() && LEFT([Text],1)="X"),"Text1",[Text]),"Text",RIGHT([Text1],1)),"Text",[Text])
    VAR __Table = EXCEPT(__Table1, __Table2)
RETURN
    CONCATENATEX(__Table,[Text],",")

k_mathana - I'll have to take a bit of a deeper look at this as I foresaw some potential problems in how I was doing this but I also need to avoid the recursive trap. I'll take a look with the sample data provided. Is there any way you could post all of your sample data with your expected result so that I can check a more complete set of data? Posted as an Excel file link or PBIX or text in a table so that I can copy and paste it easily?

k_mathana - If you are saying that you want to group these by Order, then you would simply add that to your filter criteria initially, like this:

Accumulated Text = 
    VAR __Table = 
        ADDCOLUMNS(
            FILTER(
                'Table',
                [Date]<=EARLIER([Date]) &&
                [Order] = EARLIER([Order])
            ),
            "TextX",RIGHT([Text],1),
            "Keep",IF(LEFT([Text],1)="X",0,1)
        )
    VAR __Table1 = 
        ADDCOLUMNS(
            GROUPBY(
                __Table,
                [TextX],
                "__Date",MAXX(CURRENTGROUP(),[Date])
            ),
            "FinalKeep",MAXX(FILTER(__Table,[Date]=[__Date] && [TextX] = EARLIER([TextX])),[Keep])
        )
    VAR __Cumulative = SUBSTITUTE(CONCATENATEX(FILTER(__Table1,[FinalKeep]=1),[TextX],","),",,",",")
RETURN
    IF(RIGHT(__Cumulative,1)=",",LEFT(__Cumulative,LEN(__Cumulative)-1),__Cumulative)