Sub Macro1()
Dim Lim As Double, TV() As Variant, L As Long, C As Long
Lim = Feuil1.[B3].Value
With Feuil1.[AR5:AY39]
TV = .Value
For L = 1 To UBound(TV, 1): For C = 1 To UBound(TV, 2)
If TV(L, C) > Lim Then TV(L, C) = "x"
Next C: Next L
.Value = TV
End With
End Sub