I don't know what you want .
If you want to get local computer use language , you can use Snownut2's suggest , If you want to split chinese and english , you must use other method . A Chinese characters require two bytes to store, and one letter only one byte, so you can't get a CHS Char by function ascii . However you can use the function vl-string->list , e.g.
(vl-string->list "中") --> (214 208)