´Private Sub FettSelelctionText_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button1.Click
        If Not RichTextBox1.Font.Style = FontStyle.Bold Then
            RichTextBox1.SelectionFont = New Font(RichTextBox1.SelectionFont, _
              FontStyle.Bold)
        End If
 
    End Sub