Changing font (Trebuchet MS, Calibari) in Excel programmatically C#

From what I tried, simply changing font name, size etc... on range changes font for that range:

range.Font.Name = "Arial"
range.Font.Size = 10
range.Font.Bold = true

Here is how:

    //Declare Excel Interop variables
    Microsoft.Office.Interop.Excel.Application xlApp;
    Microsoft.Office.Interop.Excel.Workbook xlWorkBook;
    Microsoft.Office.Interop.Excel.Worksheet xlWorkSheet;

    //Initialize variables
    xlApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
    xlWorkBook = xlApp.Workbooks.Add(misValue);
    xlWorkSheet = (Microsoft.Office.Interop.Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

    //Set global attributes
    xlApp.StandardFont = "Arial Narrow";
    xlApp.StandardFontSize = 10;

Focus on the 2nd line from the bottom. That sets the default font type, but I wanted to show you where xlApp came from, even if it's self explanatory.

the following worked for me, when I tried setting the default application font it did nothing so I was able to set the font name of the active sheet rows and it worked. Also worth noting I used and tested this using Excel Interop version 12

Excel.Application excelApp = new Microsoft.Office.Interop.Excel.Application();
//Create\Add workbook object
Excel.Workbooks workBooks = excelApp.Workbooks;
//Excel.Workbook
Excel.Workbook workBook = workBooks.Add(Excel.XlWBATemplate.xlWBATWorksheet);
//use worksheet object 
Excel.Worksheet workSheet = (Excel.Worksheet)excelApp.ActiveSheet;
//set default font
workSheet.Rows.Font.Name = "Arial";