highlight exact match text in cells automatically

Sociobright 

Here is a macro:

Sub MakeTextBold()
    Dim TextToFind As String
    Dim Cell As Range
    Dim CellAddress As String
    Dim Pos As Long
    Application.ScreenUpdating = False
    TextToFind = Range("A1").Value
    With Cells
        ' Change MatchCase:=False to MatchCase:=True if the search should be case-sensitive
        Set Cell = .Find(What:=TextToFind, LookIn:=xlValues, LookAt:=xlPart, MatchCase:=False)
        If Not Cell Is Nothing Then
            CellAddress = Cell.Address
            Do
                Pos = InStr(1, Cell.Value, TextToFind, vbTextCompare)
                Do While Pos
                    Cell.Characters(Start:=Pos, Length:=Len(TextToFind)).Font.Bold = True
                    Pos = InStr(Pos + 1, Cell.Value, TextToFind, vbTextCompare)
                Loop
                Set Cell = .FindNext(After:=Cell)
                If Cell Is Nothing Then Exit Do
            Loop Until Cell.Address = CellAddress
        End If
    End With
    Application.ScreenUpdating = True
End Sub