public class FormattedText 

using( var workbook = Workbook.Create( "AddFormattedText.xlsx" ) ) 
  { 
    // Gets the first Worksheet; a Workbook always contains at least 1 Worksheet. 
    var worksheet = workbook.Worksheets[ 0 ]; 
    var font = new Xceed.Workbooks.NET.Font() { Bold = true, Color = Color.Red }; 
    worksheet.Cells[ "A5" ].Value = new FormattedText( "A formatted Text", font ); 

    // Saves Workbook to disk; 
    workbook.Save(); 
  }