Workforce Trend Headcount by Assignment Status

Summary

We require a report that displays headcount for each month for the last year, but it should only count those employees with a specific assignment status.

Content

When I used the subject area "Workforce Management - Workforce Trend Real Time" on its own with Period End Headcount, I could not filter by assignment status as this subject area only displays the latest assignment data and I need historical assignment data to extract the correct Assignment Status.

So I then used one employee and performed a cross-subject area join with "Workforce Management - Worker Assignment Event Real Time" and "Workforce Management - Workforce Trend Real Time", but I see missing assignment status rows for some of the months as per below image.