Removing accented UTF8 characters from URL

[Morpheus NS]

Hello, everyone! I am using .htaccess to make my links simpler, but there is a problem.

My forum is in serbian, and I have a problem because my thread names sometimes contain accented letters (š, ć, đ, etc.). Those letters look different in URLs, or doesn't show at all. I am trying to replace them with non-accented letters (s, c, dj in this case) which are easily readable in my language. I got this code:

function google($input){
    setlocale(LC_ALL, "en_US.UTF8");
    $input = str_replace(array("'", "-", "đ"), array("", "", "dj"), $input);
    $input = mb_convert_case($input, MB_CASE_LOWER, "UTF-8");
    $input = iconv("UTF-8", "ASCII//TRANSLIT", $input);
    $input = preg_replace("#[^a-zA-Z0-9]+#", "-", $input);
    $input = preg_replace("#(-){2,}#", "$1", $input);
    $input = trim($input, "-");
    return $input;
}

which should do the trick for me, but I don't know where (in which file) do I have to put this code to work. Any idea? I am using vBulletin 4.1.1