Architectural Differences Between YSL Classic and YSL.Net Reports YSL .xls files created from the YSL.Net .xla file employ a new, simplified structure. They have no 'code- behind' in their Visual Basic for Applications (VBA) macro modules and do not hold an explicit reference to the .xla file. You should never attempt to generate these YSL reports through the YSL Classic report generating engine, because their lack of VBA code prevents them from correctly triggering and starting the YSL Classic report generating engine. YSL .xls files created from the YSL Classic .xla file retain their established reliance on 'code-behind' in their VBA macro modules. The act of opening a YSL report in Excel triggers code in the .xla file which determines if this opening occurs during run or design time. Since these YSL reports hold an explicit reference to the .xla file, you can generate them through either the YSL Classic or the YSL.Net report generating engine. In both cases, all the embedded YSL function design formulas display correctly only when opened in design mode into an instance of Excel in which the XLA has been added. If you use the YSL.Net .xla file, you can freely modify and save the YSL reports according to both YSL Classic and the simplified YSL.Net report structure. If you have a mixed portfolio of YSL.Net reports alongside YSL Classic reports, using the YSL.Net .xla file at design time is the recommended procedure. At run time, the YSL Classic reports require a YSL Classic .xla file if they are directed to generate through the YSL Classic report generating engine. In contrast, the YSL Classic .xla file performs poorly when asked to open a YSL.Net simplified .xls report.