Switch between using Dictation and Voice Command modes
This feature is available in the Simplified Chinese, English (U.S.), and Japanese language versions of Microsoft Office.
Use Dictation mode
To turn the words you speak into text, click Dictation on the Language bar or say "dictation."
Use Voice Command mode
To select menu, toolbar, dialog box (U.S. English only), and task pane (U.S. English only) items by using your voice, click Voice Command on the Language bar or say "voice command."
on the Language bar or say "dictation." 
on the Language bar or say "voice command."