Thanks for your providing us some details.
Well, it looks like ISOWEEKNUM MS Excel 2013 formula/ function is not supported by Aspose.Cells formula calculation engine. I have tested your scenario/case using a simple Excel file (attached) having ISOWEEKNUM formula applied to A1 cell of the first worksheet in the workbook. When I try to calculate the formula, I got “#NAME?” error.
e.g Sample code: Workbook wb = new Workbook(@“e:\test2\bk_isoweeknum1.xlsx”); wb.CalculateFormula(); Console.WriteLine(wb.Worksheets.Cells[“A1”].StringValue);//"#NAME?
I have logged a ticket with an id “CELLSNET-44167” for your issue. We will check if we could support ISOWEEKNUM MS Excel 2013 function for your needs.
Once we have any update on it, we will let you know here.