IHTMLTxtRange FindText depending from language?

Hi All i'm using dotnet webbrowser 2.0 in windows forms application
to show html pages, i need to highligth searched words using FindText
of IHTMLTxtRange, it don't works if i search "aereo" in a sentence
like "l'aereo".
Quote char seems to be not considered as delimiter char.

Thanks for help.
.