Email performance reports based on segmentations

Hi all

I am using the Email performance reports within the analytics platform of Marketo, and note that I can group my results by segmentation.

My only problem is that it groups it by current segmentation and not the segmentation that applied to a person prior to the email going out.

This particular segmentation is based on behaviours with EDMs.  For example, we have a 'disengaged' segments which includes those who haven't opened an email for 6 months.  As soon as they open this email, they effectivley come out of this segment and into another.

I'm finding it difficult to track the success of my campaign to the 'disengaged' group as the report is showing current segmentation. 

Any ideas how I can do this?