Bonjour Rémi, bonjour le forum,
Oui en effet désolé. Il manquait un Next I...
Sub Macro1()
Dim O As Worksheet
Dim I As Byte
Dim PL As Range
For Each O In Sheets
If Not O.Name = "Reglage" Then
For I = 13 To 56
If UCase(O.Cells(I, 13).Value) = "X" Then
Set PL = Application.Union(O.Cells(I, 1), O.Cells(I, 5), O.Range(O.Cells(I, 9), O.Cells(I, 13)))
PL.ClearContents
End If
Next I
End If
Next O
End Sub