defaults write com.microsoft.Excel AppleLanguages '("ru-RU")'
defaults write com.microsoft.Word AppleLanguages '("ru-RU")'
defaults write com.microsoft.Powerpoint AppleLanguages '("ru-RU")'
defaults write com.apple.iTunes AppleLanguages '("ru-RU")'
defaults write com.apple.TextEdit AppleLanguages '("en-US")'
Continue reading Mac OS X Hints: Set the language for a single application