Sub OneLinersII()
'In selection, replace Chr(13) with Chr(11) between all
'consecutive one-line paras, if....
Dim oPar As Paragraph 'If you dim one variable, why don't you dim all variables?
Dim oRng As Range 'You declared the range object as a variant.  Why not as a range?
  Application.ScreenUpdating = False
  Set oRng = ActiveDocument.Range
  For Each oPar In oRng.Paragraphs
    If oPar.Range.End >= oRng.End Then Exit For 'If you Exit Sub then you won't execute your ScreenUpdating line
    If Not oPar.Range.ParagraphFormat.Alignment = wdAlignParagraphCenter _
      And Not oPar.Range Like "*[0-9]*" Then
      If oPar.Range.ComputeStatistics(wdStatisticLines) = 1 Then
        Do While oPar.Next.Range.ComputeStatistics(wdStatisticLines) = 1 _
          And Not oPar.Range.Next.ParagraphFormat.Alignment = wdAlignParagraphCenter _
          And Not oPar.Next.Range Like "*[0-9]*"
          oPar.Range.Characters.Last.Text = Chr(11)
        Loop
      End If
    End If
  Next oPar
  Application.ScreenUpdating = True
  Set oRng = Nothing: Set oPar = Nothing
lbl_Exit:
  Exit Sub
End Sub