LetterContent.RecipientGender (Word)

Returns or sets the recipient's gender, if known. Not used in the U.S. English version of Microsoft Word. Possible return values are wdGenderFemale - Female gender, wdGenderMale - Male gender, wdGenderNeutral - Neutral gender, wdGenderUnknown - Unknown gender.

This property may not be available to you, depending on the language support (U.S. English, for example) that you've selected or installed.

ActiveDocument.CreateLetterContent.RecipientGender = wdGenderFemale