Finding the Added and Deleted Codes out of the two sets of Codes Entered

see if this works for you:

Sub t()
Dim c As Range, spl As Variant, i As Long, txt As String
    For Each c In Range("A2", Cells(Rows.Count, 1).End(xlUp))
        spl = Split(c.Value, ",")
        For i = LBound(spl) To UBound(spl)
            If InStr(c.Offset(, 1).Value, spl(i)) = 0 Then
                txt = txt & ", " & spl(i)
            End If
        Next
        If txt <> "" Then
            c.Offset(, 2) = Right(txt, Len(txt) - 2)
        End If
        txt = ""
        spl = Split(c.Offset(, 1).Value, ",")
        For i = LBound(spl) To UBound(spl)
            If InStr(c.Value, spl(i)) = 0 Then
                txt = txt & ", " & spl(i)
            End If
        Next
        If txt <> "" Then
            c.Offset(, 3) = Right(txt, Len(txt) - 2)
        End If
        txt = ""
    Next
End Sub