Qrew LegendI don't think that approach will work. I think that you will need to create a field to hold the previous status and initialize it with the value of the current status. The easiest way to do that is to make a formula field equal to the status and then change it to be a data entry field.
Then you will need to have a pipeline to maintain the previous status value by firing whenever the status changes and writing out the previous status with syntax similar to what you posted.
Then you will have a pipeline trigger on status change and will be able to have two solid fields to compare, the [Status] and the [Previous Status] fields in your table.
