Cómo decorar rangos en MS-Word

I am building a Word Add-in which scans the document for misplaced words. It works like a spell checker by using a dictionary. The spell checker in Word places a curly red line beneath the word and I want to decorate my misplaced words in the same way or by a customized symbol placed on the actual word in the document window.

How can I do that? Where to find documentation on the issue?

It is very important that this decoration don't change the actual document, so "highlight","Bold" or "italics" is not an option.