Research.FavoriteService Property (Word)
Returns or sets a String that specifies the favorite research service.
The String that is set or returned for this property specifies the GUID of the favorite research service.
Setting this property has the same effect as choosing a favorite research service through the Research Options dialog in Word 2010.
The GUIDs for all installed research services can be located in the HKCU\Software\Microsoft\Office\14.0\Common\Research\Sources registry key.