Sub test()
Dim P As Range, xV$, col&, NewNum
Set P = [A6:D6]
Qui = InputBox("Choisir personne?", "Test", "Marion")
xV = "" & Chr(42) & CStr(Qui) & Chr(42) & ""
col = Application.Match(xV, P, 0)
NewNum = Cells(Rows.Count, col).End(3) + 1
If MsgBox("Nouveau N° de devis = " & NewNum, vbYesNo) = 6 Then
Cells(Rows.Count, col).End(3)(2) = NewNum
End If
End Sub