I'm not sure if I understand it correctly but you can filter out table with start date and reporting date.
This would be a scope of report (assuming that end date is earlier than reporting date). If this assumption is not correct, just switch end date with reporting date.
Now, for calculating differences, do something like this:IIF([EventDate]>=[EndDate],[Measure],NULL)
This calc will only show values between end date and reporting date.
[EventDate] is a field on which filtering and time dimension is based on.
It would be easier for various helpers to help if enough dummy sample data was included - preferably in an Attached Packaged Workbook - with examples of what expected filtered output should be and thus illustrate what you mean.
I assume it will look something like Slowly changing dimension - Wikipedia but think more rows are needed than shown in Wikipedia example.