Hi,
In versions of KoolReport prior to 4, AccumulativeColumn worked as follows where the target was actually performed as a calculation.
->pipe(new AccumulativeColumn(array("Running Total"=>"Column1 - Column2")))
In version 4+, it appears that this calculation is not performed but assumes that 'Column1 - Column2' is the actual column name.
I got around this by performing the calculation in the SQL but it is a pain to refactor into many reports.