Sub ReplaceInFolder()
    Dim strPath As String
    Dim strFile As String
    Dim wbk As Workbook
    Dim wsh As Worksheet
    Dim strFind As String
    Dim strReplace As String
    strFind = InputBox("Enter text to find")
    If strFind = "" Then
        MsgBox "No find text specified!", vbExclamation
        Exit Sub
    End If
    strReplace = InputBox("Enter replacement text")
    With Application.FileDialog(msoFileDialogFolderPicker)
        If .Show Then
            strPath = .SelectedItems(1)
        Else
            MsgBox "No folder selected!", vbExclamation
            Exit Sub
        End If
    End With
    If Right(strPath, 1) <> "\" Then
        strPath = strPath & "\"
    End If
    Application.ScreenUpdating = False
    strFile = Dir(strPath & "*.xls*")
    Do While strFile <> ""
        Set wbk = Workbooks.Open(Filename:=strPath & strFile, AddToMRU:=False)
        For Each wsh In wbk.Worksheets
            wsh.Cells.Replace What:=strFind, Replacement:=strReplace, _
                LookAt:=xlWhole, MatchCase:=False
        Next wsh
        wbk.Close SaveChanges:=True
        strFile = Dir
    Loop
    Application.ScreenUpdating = True
End Sub

-----------

ví dụ: thay giám đốc thành tổng giám đốc:

"Gi" & ChrW(225) & "m " & ChrW(272) & ChrW(7889) & "c"

"T" & ChrW(7893) & "ng gi" & ChrW(225) & "m " & ChrW(273) & ChrW(7889) & "c"

---

Sub Macro2()
'
' Macro2 Macro
'

'
    Cells.Replace What:="Gi" & ChrW(225) & "m " & ChrW(272) & ChrW(7889) & "c", Replacement:="T" & ChrW(7893) & "ng gi" & ChrW(225) & "m " & ChrW(273) & ChrW(7889) & "c", LookAt:=xlPart _
        , SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
        ReplaceFormat:=False
End Sub

'---

Sub TextBoxReplace()
    Dim shp As Shape
    Dim sOld As String
    Dim sNew As String

    'Change as desired
    sOld = "g"
    sNew = "g1"
    On Error Resume Next
    For Each shp In ActiveSheet.Shapes
        With shp.TextFrame.Characters
            .Text = Application.WorksheetFunction.Substitute( _
              .Text, sOld, sNew)
        End With
    Next
End Sub