Sub ok()
Dim i As Integer
Dim plage As Range
Dim c As Range
Dim ref As String
For i = 1 To 12
ref = Sheets("Feuil2").Range("A" & i)
Feuil3.Activate
Set plage = Range(ref)
For Each c In plage
If Not IsNumeric(c) Then c.Value = "OK"
Next
Next i
End Sub