Sub Copie_M()
Dim c As Range
Set c = Cells.Find("M", , xlValues, xlWhole)
If c Is Nothing Then Exit Sub
If MsgBox("Reporter les données du mois M sur le mois M-1 ?", vbYesNo) = vbNo Then Exit Sub
Application.ScreenUpdating = False
For Each c In Range(c(2), Cells(Rows.Count, c.Column).End(xlUp))
If IsNumeric(CStr(c)) And Not c(1, 0).HasFormula Then
Range(Cells(c.Row, 3), c(1, 0)).Copy Cells(c.Row, 2) 'transfert à gauche
c(1, 0) = c
End If
Next
End Sub