Edit the "newbloguser"

I`m working on a multisite installation of wordpress 3.0. When I let administrators ad new users to thiere blogs, and the new user confirms by clicking on the link in the email, that has been sent, the user then gets this message: <em>You have been added to this site. Please visit the homepage or login using your username and password</em>

That is all good, but I want to translate those lines in to another language, and I can`t find the strings in the wordpress translationfiles, so maybe I should just hardode it in to the script, but where should I add/change those lines? Where do I find the /newbloguser page in the script?

Hope you can help….thanks!