Absence and assignment details as of an effective date

Content

Hi,

I'm building an anaylsis in the Absence Real Time Subject Area using fields from the Worker folder and some key information from the Assignment Absence Details.  The analysis is also date prompted based on the Start/End Date of the absence.  This works fine however the report appears to be pulling back the worker's current assignment details. 

So for example at the moment im getting;

John Smith - Finance - Sick 1-3 Jan 2015

John Smith - Finance - Sick 8-15 Feb 2016

In Jan 2015 John was actually working for Marketing so what I want to show is;

John Smith - Marketing - Sick from 1-3 Jan 2015