Sub Highlight_Duplicate()
    Dim ws As Worksheet
    Dim cell As Range
    Dim myrng As Range
    Dim clr As Long
    Dim lastcell As Range
    Dim i As Long
    Dim lastrow As Long

    Set ws = ThisWorkbook.ActiveSheet

    'Vung can danh dau gia tri trung nhau
    Set myrng = ws.Range("C4:F" & Range("C" & ws.Rows.Count).End(xlUp).Row)

    With myrng
        Set lastcell = .Cells(.Cells.Count)
    End With

    myrng.Interior.ColorIndex = xlNone
    clr = 3

    For Each cell In myrng
        'Kiem tra so gia tri trung nhau trong vung, neu co hai gia tri trung nhau tro len thi thuc hien
        If Application.WorksheetFunction.CountIf(myrng, cell) > 1 Then
            'Neu la o dau tien cua cac gia tri trung nhau trong vung
            If myrng.Find(what:=cell, lookat:=xlWhole, MatchCase:=False, after:=lastcell).Address = cell.Address Then
                'Thiet lap mau
                cell.Interior.ColorIndex = clr
                clr = clr + 1
                i = i + 1
            Else
                'Thiet lap mau tu o thu 2 voi cac gia tri trung nhau
                cell.Interior.ColorIndex = myrng.Find(what:=cell, lookat:=xlWhole, MatchCase:=False, after:=lastcell).Interior.ColorIndex
            End If
        End If
    Next

     'Lay dong cuoi cung cua vung du lieu
    lastrow = Cells(Rows.Count, "A").End(xlUp).Row
    Range("A" & lastrow + 2).Value = "Tong so co " & i & " gia tri trung nhau"
End Sub