I need to create a custom text editor, which will be editing device specific files. The files are text files and supposed to contain a subset of the low ASCII characters. Some of the characters should display as strings rather than as their normal display value in the loaded windows character set. I need to display tab characters in their expanded representation as spaces. The files use Form Feeds (x0C) to mark pages. These need to be represented on their own line as a string of dashes. Can this type of character rendering control be accomplished with the RichTextBox control and it's txtformatproviders? If so what would be involved (or is there an example in the SDK's I should look at?