Hi guys

I have an attachment which colours the repeated entries in Columns A and B
I want to add some lines of code that give me a message box to accept the new repeated entries or not
The code is :
Private Sub Worksheet_Change(ByVal Target As Range)
Dim R As Integer, C As Integer
If Not Intersect(Target, Range("A1:B100")) Is Nothing Then
    Application.ScreenUpdating = False
    C = Target.Column
    For R = 1 To 100
        If Cells(R, C) <> "" And Application.CountIf(Range(Cells(1, C), Cells(100, C)), Cells(R, C)) > 1 Then
            Cells(R, C).Interior.ColorIndex = 40
        Else
            Cells(R, C).Interior.ColorIndex = xlNone
        End If
    Next
    Application.ScreenUpdating = True
End If
End Sub