See the article "Retrieving Data from a Named Range in Excel using DAO" at:

http://www.word.mvps.org/FAQs/InterDev/XLToWordWithDAO.htm

This should do it:

'Set a reference to the Microsoft DAO 3.6 Object Library under
Tools>References
Dim db As DAO.Database
Dim rs As DAO.Recordset
Dim oldnumber As String
Dim newnumber As String
Dim myrange As Range

'Change path\filename
Set db = OpenDatabase("C:\Test\Book1.xls", False, False, "Excel 8.0")
'In Excel, assign the name New for Old to the range of numbers, including
the column headings
Set rs = db.OpenRecordset("SELECT * FROM `NewforOld`")

While Not rs.EOF
   oldnumber = rs.Fields(0).Value
   newnumber = rs.Fields(1).Value
   Selection.HomeKey wdStory
   Selection.Find.ClearFormatting
   With Selection.Find
       Do While .Execute(FindText:=oldnumber, MatchWholeWord:=True,
MatchWildcards:=False, Wrap:=wdFindStop, Forward:=True) = True
           Set myrange = Selection.Range
           Selection.Collapse wdCollapseEnd
           Selection.MoveRight wdWord, 1
           myrange.Text = oldnumber & "/(" & newnumber & ")"
       Loop
   End With
   rs.MoveNext
Wend

rs.Close
db.Close

Set rs = Nothing
Set db = Nothing