How to find the Story points completed for the last but one completed sprint

Hi All,
I have a requirement, where i need to calculate the velocity variance, for which the formula is
Current sprint story points completed / previous sprint story points completed.
For getting the current sprint data, we can get it by
[Measures].[Sprint story points completed]
But for getting the last but one sprints data, how do we get?
For example, we have 6 completed sprints
So for every sprint, we need to calculate velocity variance.
For Sprint 2 variance, it would be sprint 2 story points completed / sprint 1 story points completed
Similarly for Sprint 3 variance, it would be sprint 3 story points completed / sprint 2 story points completed.

So let me know how to calculate the previous completed sprint story points



The previous sprint from the same sprint board can be accessed using the PrevMember function.

The following formula provides the completed story points for the previous sprint:

([Measures].[Sprint Story Points completed],

Janis, eazyBI support