Sub DebFin()
Dim DerLig As Long, i As Long, Compt As Integer, Deb As Integer, Fin As Integer, Mois As String
Mois = InputBox("Entrez le mois recherché")
If Mois = "" Then Exit Sub
DerLig = Worksheets("Base").Range("A" & Rows.Count).End(xlUp).Row
For i = 2 To DerLig
If Trim(Cells(i, 4)) = Mois Then
Compt = Compt + 1
If Compt = 1 Then Deb = i
End If
Next
Fin = Deb + Compt - 1
MsgBox "Plage du mois de " & Mois & " lignes " & Deb & " à " & Fin
End Sub