title: rtf change font size
body: <p>I am trying to perform edit functions in a RichTextBox on a C# (Windows Forms) application.
  I would like to be able to select any number of text characters in the script then change targeted font characteristics.<br>
  The trouble I have is that each characters font properties  may be set to different font. In this case the textbox ignores the event that I request.   </p>
  
  <p>How can I solve my problem?</p>