There are several commercial applications which support this feature. One of them is WinGrep. It supports many power features. However, when it's tested on my system, it could not search properly Korean characters. Here, I want to recommend IceTeaReplacer. It's simple to use. Most of all, it's free. And this application search and replace text within Word and Excel. (Although it's a free version, it supports Korean characters without any problem.)
