Sub ReplaceStringInExcelFiles()

    Dim MyFile As String
    Dim FilePath As String
    Dim orig As String
    Dim news As String
    Dim wb As Workbook, ws As Worksheet

    orig = "dog"
    news = "cow"

    FilePath = "F:\DESTOP00\1\"
    MyFile = Dir(FilePath & "*.xls*")

    Do While Len(MyFile) > 0
        Set wb = Workbooks.Open(FilePath & MyFile) '<< assign the workbook to wb
        'Loop over the worksheets
        'Note: no need to activate/select
        For Each ws In wb.Worksheets
            ws.UsedRange.Cells.Replace what:=orig, _
                            Replacement:=news, _
                            lookAt:=xlPart, SearchOrder:=xlByRows, _
                            MatchCase:=False

     'xu ly cho textbox                       
    On Error Resume Next
    For Each shp In ws.Shapes
    xValue = shp.TextFrame.Characters.Text
    shp.TextFrame.Characters.Text = VBA.Replace(xValue, orig, news, 1)
    Next
                            
                            
        Next ws
        ActiveWorkbook.Close savechanges:=True
        MyFile = Dir
    Loop

End Sub