Time slicer - how to get information of filtered values

[Nilsoo]

Hi,
my problem is the following:
I want to filter my data using a time slicer. In general, kneed to know how many values there are at the beginning and at the end of the selected date range.  The problem is I need to the amount of values that are sorted out until the initial point of the selected date range to calculate.
Of course, I could calculate the total amount of values and subtract the amount of displayed values to get the amount of filtered values if the end date is not adjusted but this will not work if you adjust the starting and ending point.
Anyone has an idea how to solve this?

Thanks, in advance.

Example

Date     Sales
1.1        10
2.1        20

3.1         5

4.1         10

5.1         5

 
Now the filter is adjusted and the selected date range is 2.1-4.1. How can I get the the total revenue for 2.1 (which is 30) and for 4.1 (45)?