Private Sub btnRun_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnRun.Click
    Dim workbook As Workbook = New Workbook()
    Dim sheet As Worksheet = workbook.Worksheets(0)
 
    Dim fontBold As ExcelFont = workbook.CreateFont()
    fontBold.IsBold = True
 

    Dim fontUnderline As ExcelFont = workbook.CreateFont()
    fontUnderline.Underline = FontUnderlineType.Single
    
    Dim fontColor As ExcelFont = workbook.CreateFont()

    fontColor.KnownColor = ExcelColors.Green

    Dim richText As RichText = sheet.Range("A1").RichText
    richText.Text = "Bold and underlined and colored text"
    richText.SetFont(0,3,fontBold)
    richText.SetFont(9,18,fontUnderline)
    richText.SetFont(24,30,fontColor)

    workbook.SaveToFile("Sample.xls")
    ExcelDocViewer(workbook.FileName)
End Sub