Under control of MS Excel - how to compose rich text sentences (with mixed font features in the same sentence) and automatically copy-paste the sentences to other office applications?

The standard UserForm does not allow mixed fonts to be entered into the same Text control. Under excel vba control, I want to type simple rich text for scientific notation: superscript, subscript, italic, with SYMBOL font plus one or just a few standard fonts, like Calibri, or Tahoma, for example.
These formatting features to be applied together (in various combinations) to just a sentence or two, in each instance.

If this is possible, I'd then want to use vba automation to copy the rich text output and paste it into another office format: particularly into a shape object in MS Visio. I'm aware that mixed text can be composed in Visio shapes directly, but in my excel+visio automation piece, it would greatly help the user to compose rich text outside the visio application.

Is there a way of achieving this?

Thanks
Kelvin