Programmatically add rtf hyperlink to rtf file

I need to create a method that receive a string with a filepath and I have to update a rtf file inserting that string as a hyperlink. The problem is how to translate the filename into a clickable rtf link in C# to add it to the file. I tried to use a RichTextBox initializing the text property with the rtf file text but I don't know how to add the link. And I tried doing it directly in rtf but the link don't target to the filepath because I need a txfielddata with some kind of hexadecimal code that I don't know how to generate it. I'm totally stuck...

Any idea?