text: public SheetRefEvaluator GetSheetEvaluator(int sheetIndex){if (sheetIndex < _firstSheetIndex || sheetIndex > _lastSheetIndex){throw new ArgumentException("Invalid SheetIndex: " + sheetIndex +" - Outside range " + _firstSheetIndex + " : " + _lastSheetIndex);}return _sheetEvaluators[sheetIndex - _firstSheetIndex];}