For reliability I'd rather go with system-language or even better GeoIP...
Anyways, this code should do it.
Code:
<s c r i p t>
targetLanguage = "COUNTRY-CODE HERE";
targetURL = "http://URL.HERE";
bLang = navigator.Language ? navigator.Language : navigator.userLanguage;
if (bLang.indexOf(targetLanguage) >= 0) window.location.href=targetURL;
</s c r i p t>
Take the spaces out of the s c r i p t tags of course and enter CountryCode and URL