What you are asking cannot be done with formulas. Neither with
conditional formatting, because you want formatting at text and not
cell level.

The following marco will highlight the word srch in all cells in the
range C1:D10 of Sheet1:

Sub Highlight(srch As String)
Dim dta As Range, c As Range

Set dta = Sheets("Sheet1").Range("C1:D10")
For Each c In dta
If InStr(1, c.Value, srch) Then
With c.Characters(Start:=InStr(1, c.Value, srch),
Length:=Len(srch)).Font
.ColorIndex = 41
End With
End If
Next c
End Sub

HTH
Kostis Vezerides