Adds all the numbers in a range of cells.
This method doesn't have any parameters.
builder.CreateFile("xlsx");
var oWorksheet = Api.GetActiveSheet();
var oFunction = Api.GetWorksheetFunction();
oWorksheet.GetRange("A1").SetValue(oFunction.SUM(145, 37, 236, 69, 567, 92));
builder.SaveFile("xlsx", "SUM.xlsx");
builder.CloseFile();