Sub TelNettoyage()
Dim cel As Range
Dim SearchString, SearchChar, MyPos
SearchChar = "-"
For Each cel In Range("M2" & Range("M65535").End(xlUp).Row)
SearchString = cel.Text
MyPos = InStr(SearchString, SearchChar)
If MyPos = 0 Then
cel.Value = Left(cel.Value, 1) & "-" & Right(cel.Value, Len(cel.Value) - 1)
End If
Next cel
End Sub