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One way you can do it is with a macro. For example, if cell A1 has the data that changes. You can use this code:
Private Sub Worksheet_SelectionChange()
Range("A3").Value = Range("A2").Value
Range("A2").Value = Range ("A1").Value
End Sub
Then in cell A4 you would have:
=A2 - A3
This will show you the change. You can even use conditional formatting to change the colors.