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So far, in addition to the highlight effect after selected characters, I do not find the way to highlight the specific charactes in Text Box (ActiveX Control).
Here is a similar thread "Add Text Formatting to a 'Text Box with ActiveX Control' in word" you could have a look, especilaly the replies from CharlesKenyon (IA).
That try to use Content Control or other controls as a workaround.
Thanks for your undersandting.
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