Range.LanguageID Property (Word)
Returns or sets a WdLanguageID constant that represents the language for the specified range. Read/write.
An expression that represents a Range object.
Some of the WdLanguageID constants may not be available to you, depending on the language support (U.S. English, for example) that you’ve selected or installed.
This example formats the second paragraph in the active document as French and then adds a new custom dictionary that will be used on the French text.
ActiveDocument.Paragraphs(2).Range.LanguageID = wdFrench
Set myDictionary = CustomDictionaries.Add(Filename:="French.dic")
.LanguageSpecific = True
.LanguageID = wdFrench