HtmlAgilityPack create node from text

Question

Let's assume I have this

<div>
    <p>Bla bla bla specialword bla bla bla</p>
    <p>Bla bla bla bla bla specialword</p>
</div>

I want to replace the word specialword from my html with a node, for example <b>specialword</b>. This is easy using string replacement, but I want to use the Html Agility Pack features.

Thanks.