Edit|replace won't work (as you've seen).

You could use a macro, though:

Saved from a previous post:

Option Explicit
Option Compare Text
Sub testme()

   Application.ScreenUpdating = False

   Dim myWords As Variant
   Dim myRng As Range
   Dim foundCell As Range
   Dim iCtr As Long 'word counter
   Dim cCtr As Long 'character counter
   Dim FirstAddress As String
   Dim AllFoundCells As Range
   Dim myCell As Range
       
   'add other words here
   myWords = Array("widgets", "assemblies", "another", "word", "here")
   
   Set myRng = Selection
   
   On Error Resume Next
   Set myRng = Intersect(myRng, _
                 myRng.Cells.SpecialCells(xlCellTypeConstants, xlTextValues))
   On Error GoTo 0
   
   If myRng Is Nothing Then
       MsgBox "Please choose a range that contains text constants!"
       Exit Sub
   End If
   
   For iCtr = LBound(myWords) To UBound(myWords)
       FirstAddress = ""
       Set foundCell = Nothing
       With myRng
           Set foundCell = .Find(what:=myWords(iCtr), _
                               LookIn:=xlValues, lookat:=xlPart, _
                               after:=.Cells(1))
                               
           If foundCell Is Nothing Then
               MsgBox myWords(iCtr) & " wasn't found!"
           Else
               Set AllFoundCells = foundCell
               FirstAddress = foundCell.Address
               Do
                   If AllFoundCells Is Nothing Then
                       Set AllFoundCells = foundCell
                   Else
                       Set AllFoundCells = Union(foundCell, AllFoundCells)
                   End If
                   Set foundCell = .FindNext(foundCell)
                   
               Loop While Not foundCell Is Nothing _
                   And foundCell.Address <> FirstAddress
           End If
                   
       End With
       
       If AllFoundCells Is Nothing Then
           'do nothing
       Else
           For Each myCell In AllFoundCells.Cells
               For cCtr = 1 To Len(myCell.Value)
                   If Mid(myCell.Value, cCtr, Len(myWords(iCtr))) _
                             = myWords(iCtr) Then
                       With myCell.Characters(Start:=cCtr, _
                                 Length:=Len(myWords(iCtr)))
                           .Font.ColorIndex = 3
                           .Font.Bold = True
                       End With
                   End If
               Next cCtr
           Next myCell
       End If
   Next iCtr
   Application.ScreenUpdating = True

End Sub

If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm

This portion:

                       With myCell.Characters(Start:=cCtr, _
                                 Length:=Len(myWords(iCtr)))
                           .Font.ColorIndex = 3
                           .Font.Bold = True
                       End With

Changes the color and the boldness.

You may want to save first--so you can close without saving if you don't want to
keep the formatting changes.  Remember this kind of formatting only works on
text cells--not formulas--not numbers.