Plain text, Unicode do not define subscripts/superscripts for every character. You need some kind of formatting text. If this is HTML, this is trivial: you can use
(Why, why did you neglect to tag application type or UI library you use?! don't blame me for an approximate answer, find further detail by yourself.)
If this is not a Web application or some HTML document generated by your application, you can use rich text box (exact type depends on you UI library, look it up).
Also, there are some components on the CodeProject which allow to render HTML in your Windows application:
A Professional HTML Renderer You Will Use
WPF HTML Supported TextBlock