The usage description for CountDistinct is like CountDistinct("FieldName", 'Level'), but when I use CountDistinct("EXLAREA_CONCENTRATION_CODE", 'Current'), I get an error saying 'Aggregate expressions are not allowed in fields'." And I have a question about using the CountDistinct formula in AdHoc report. I want to calculate the distinct count of 'EXLAREA_CONCENTRATION_CODE' where EXLAREA_CONCENTRATION_CODE is not 'GERAL'. Any help would be greatly appreciated.