Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim c As Range
For Each c In Range("C2:C" & Range("C65536").End(xlUp).Row)
If c = "NUL" Then
c.Offset(0, -2).Font.ColorIndex = 3
Else
c.Offset(0, -2).Font.ColorIndex = xlAutomatic
End If
Next c
End Sub