Sub SearchMultipleWords()
  Dim MyAr() As String, strToFind As String
  strToFind = "Background, Methods, Results, Conclusion"
  MyAr = Split(strToFind, ",")
  For i = LBound(MyAr) To UBound(MyAr)
    With ActiveDocument.Range.Find
      .ClearFormatting
      .Replacement.ClearFormatting
      .Text = MyAr(i)
      .Replacement.Style = "B12"
      .Forward = True
      .Wrap = wdFindContinue
      .Execute Replace:=wdReplaceAll
    End With
  Next i
End Sub