Это может помочь:
Sub InsertSeqNo()
Dim Rng As Range
Set Rng = ActiveDocument.Range
Do While Rng.Find.Execute(FindText:="Figure X", Forward:=True, Format:=False, Wrap:=wdFindStop) = True
Rng.MoveStart Unit:=wdCharacter, Count:=7
Rng.Fields.Add Range:=Rng, Type:=wdFieldEmpty, Text:="SEQ Fig \* ARABIC", PreserveFormatting:=True
Loop
ActiveDocument.Fields.Update
End Sub