var instance = new GcSpread.Sheets.Calc.EvaluateContext(source,
                                                       arrayFormula,
                                                       baseRow,
                                                       baseColumn,
                                                       rowCount,
                                                       columnCount,
                                                       activeRow,
                                                       activeColumn);
var value; // Type: number
value = instance.getValue(source, row, column);