Filtering BEx query by measure

Good day experts.

I have cube with to dates start date (SD) and end date (ED) as charachteristics. ED is not obligatory and can be blank.

I have to calculate difference between two dates, if ED is blank between current date (CD) and SD = DIFF.

And filter query by this calculated value DIFF. For example from 0 to 100 days.

Problem is Query should not contain detailed view, but work for aggregates.

For example.

                           DIFF          VALUE

Institution 1          99               10

Institution 1          1                 30

Institution 1          101              100

Institution 1          25                37

Institution 2          105               20

Institution 2          110               35

Institution 2          13                 41

Institution 2          14                12

Result of the query should be for measure range from 0 to 100:

                         VALUE

Institution 1          77

Institution 2          53

Total                    130

I followed topic

Convert a Characteristic into a Key Figure (BEx)

and converted CHARs to KEYS.

Created condition with restriction, and assignment to both dates.

Query works but only for detailed view, which contains both dates.

I even created new cube, with dates as key figures and calculated key figure - result is same.

Query works only if both dates are in selection.

Please help me - how to make query work for aggregated view?

Thank you.