Macro for more than 3 conditional formats

Hello, I recently used the attached link to circumvent the limitation of excel's conditional formating (i.e. 3 conditions) and used the macro to extend conditional formatting to multiple conditions. While the macro works fine the minute I enable protection on the worksheet, the macro consistently produces "Run TIme Error 1004.. Unable to set the colorindex property of the interior class. The input cells are not protected, but they do have data validation. Any one have any ideas.




Private Sub Worksheet_Change(ByVal Target As Range)
Set MyPlage = Range("R7:R1000")
For Each Cell In MyPlage

If Cell.Value = "Extreme" Then
Cell.Interior.ColorIndex = 3
End If
If Cell.Value = "Hight" Then
Cell.Interior.ColorIndex = 4
End If
If Cell.Value = "Medium" Then
Cell.Interior.ColorIndex = 18

End If
If Cell.Value = "Low" Then
Cell.Interior.ColorIndex = 6
End If

If Cell.Value <> "Extreme" And Cell.Value <> "Hight" And Cell.Value <> "Medium" And Cell.Value <> "Low" Then
Cell.Interior.ColorIndex = xlNone
End If

Next
End Sub

https://ccm.net/forum/affich-21716-conditional-formatting-more-than-3-in-excel