Filtering in DAX formula

[LisaBureau]

I have a calendar showing the last day of each month from Jan 2015 to Dec 2027 ('Calendar'[Dates])

I have an actual cost table with dates ('Actual Costs'[Date]) - also last day of each month -

1. from Feb 2021 Measure = CALCULATE(FIRSTDATE('Cost Graphs'[Date]),('Cost Graphs'[Cost Actual]>0))

2. to July 2023 - Measure = CALCULATE(LASTDATE('Cost Graphs'[Date]),('Cost Graphs'[Cost Actual]>0))

I want a graph with 'Calendar'[Dates] as my x-axis giving the cumulative of 'Cost Graphs'[Value] - Measure = sum('Cost Graphs'[Cost Actual]) - but only between the First Date and Last Date - otherwise it must be blank.

So I am trying to follow online, but am confused about which "date" goes where.  This is where I am at but it is soooo not working:

Cumulative Actual = IF(SELECTEDVALUE('Calendar'[Dates])>[Cumulative Last Actual Date],BLANK(),IF(SELECTEDVALUE('Calendar'[Dates])<[Cumulative First Actual Date],BLANK(),

CALCULATE('Cost Graphs'[Cost Actual Total],FILTER(ALLSELECTED('Calendar'[Dates],'Cost Graphs'[Date]<=[Cumulative Last Actual Date])))))

Please help.

[Greg_Deckler]

@LisaBureau First, I would clean up the logic using SWITCH(TRUE(), ...) instead of nexted if statements. Second, have a look at this article on running totals and the associated video. Third, posting sample data and expected output would be extremely helpful.

Better Running Total - Microsoft Fabric Community

[LisaBureau]

I need it to graph only between my First and Last date - I think it is the "filter" portion I'm not getting.  How do I filter my Calendar dates to only be between my First and Last on my x-axis, is really my question?