HighlightMergeFields Property
True to highlight the merge fields in a document. Read/write Boolean.
expression.HighlightMergeFields
expression Required. An expression that returns one of the objects in the Applies To list.
Example
This example turns off highlighting merge fields in the active document.
Sub HighlightFields()
ActiveDocument.MailMerge.HighlightMergeFields = False
End Sub