BoxText with various styles

Hello,

I'd like to create a boxText and apply different styles (font, fill color, etc...) to a selection of characters in the boxText using the script only. It's possible to do this through the UI (by selecting certain characters and changing the style in the character panel), but I haven't found any solutions to change the style of a selection of characters within the boxText by script alone.

Is it possible to select and modify certain characters in the boxText (and not all the characters in one boxText) using only the script? If so, how can I go about doing this?

Thanks for help!