Not built into excel. You could use a macro, though:
Option Explicit
Sub testme01()
Dim myWords As Variant
Dim myCell As Range
Dim myRng As Range
Dim FirstAddress As String
Dim iCtr As Long
Dim letCtr As Long
On Error Resume Next
Set myRng = Intersect(Selection, _
Selection.Cells _
.SpecialCells(xlCellTypeConstants, xlTextValues))
On Error GoTo 0
myWords = Array("test", "bold", "hilight")
If myRng Is Nothing Then
MsgBox "No Text Cells found in Selection"
Exit Sub
End If
For iCtr = LBound(myWords) To UBound(myWords)
With myRng
Set myCell = .Find(What:=myWords(iCtr), After:=.Cells(1), _
LookIn:=xlValues, LookAt:=xlPart, _
SearchOrder:=xlByRows, _
SearchDirection:=xlNext, _
MatchCase:=False)
If Not myCell Is Nothing Then
FirstAddress = myCell.Address
Do
For letCtr = 1 To Len(myCell.Value)
If StrComp(Mid(myCell.Value, letCtr, _
Len(myWords(iCtr))), _
myWords(iCtr), vbTextCompare) = 0 Then
myCell.Characters(Start:=letCtr, _
Length:=Len(myWords(iCtr))) _
.Font.FontStyle = "Bold"
End If
Next letCtr
Set myCell = .FindNext(myCell)
Loop While Not myCell Is Nothing _
And myCell.Address <> FirstAddress
End If
End With
Next iCtr
End Sub
You can just put the words you need to highlight in this line:
myWords = Array("test", "bold", "hilight")
(one word is ok, too.)
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm