Sub essai()
Dim Cell As Range, y As String, i As Integer
Application.ScreenUpdating = False
For Each Cell In Range("C2:W50")
If Cell.Value <> "" Then
y = ""
For i = 1 To Len(Cell.Value)
If Mid(Cell.Value, i, 1) = LCase(Mid(Cell.Value, i, 1)) Then
y = y + Mid(Cell.Value, i, 1)
End If
Next i
Cell.Value = IIf(y = "", "OK", Trim(y))
End If
Next
Application.ScreenUpdating = True
End Sub