Sub CheckTherefore()
Application.ScreenUpdating = False
Randomize Timer
Dim strWords As String, i As Long, j As Long, k As Long, bCap As Boolean
strWords = "therefore,in other words,hence,so we can conclude that," & _
   "on this basis we conclude that,that is,so we conclude that"
i = UBound(Split(strWords, ",")) + 1
With ActiveDocument.Range
  With .Find
    .Text = "therefore"
    .Forward = True
    .Wrap = wdFindStop
    .Format = False
    .MatchCase = False
    .MatchWholeWord = True
    .MatchWildcards = False
    .MatchSoundsLike = False
    .Execute
  End With
  Do While .Find.Found
    bCap = (UCase(.Characters.First) = .Characters.First)
    Do While j = k
      j = Int(Rnd() * i)
    Loop
    .Text = Split(strWords, ",")(j)
    k = j
    If bCap = True Then .Characters.First = UCase(.Characters.First)
    .Collapse wdCollapseEnd
    .Find.Execute
  Loop
End With
Application.ScreenUpdating = False
End Sub