expression.AddHorizontalInVertical(Range, Text)
expression Required. An expression that returns one of the objects in the Applies To list.
Range Required TextRange object. The text range at which to insert the horizontal text.
Text Required String. The text to be horizontally inserted.
Example
This example horizontally inserts the text "horizontal test" after the existing vertical text in shape one on page one of the active publication.
Dim rngTemp As TextRange
Dim fldTemp As Field
With ActiveDocument.Pages(1).Shapes(1)
Set rngTemp = .TextFrame.TextRange.InsertAfter("")
Set fldTemp = .TextFrame.TextRange.Fields _
.AddHorizontalInVertical(Range:=rngTemp, Text:="horizontal test")
End With