Try:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim i As Long, Rng As Range
With ActiveDocument.Range
For i = 1 To .Sentences.Count
With .Sentences(i)
.InsertBefore " "
Set Rng = .Characters.First
Rng.Collapse wdCollapseStart
.Fields.Add Range:=Rng, Type:=wdFieldSequence, _
Text:="No.", PreserveFormatting:=False
End With
Next
End With
Set Rng = Nothing
Application.ScreenUpdating = True
End Sub
With this code, the numbering is applied via SEQ fields. Had I hard-coded the numbers, you would have had to re-number every sentence after the first one that gets mis-numbered; this way simply deleting the offending numbers then updating the fields (e.g. Ctrl-A, F9) - which you can leave till all the offending numbers have been deleted - is all you need do.