is it possible to change the content of qwebview before rendering ?

I want to make some changes to the content of my own webbrowser before it rendering in QWebview

for example ,to enlarge font size for some special words:

"hello"

will be change to "<font bold>hello<font>"

I have tried the function sethtml, but it will cause qwebview render twice:
after all the content retrieved from the website
get the content from qwebview, revise it ,then use sethtml to update the qwebview.

is there any better way to do that?