Option Explicit
Private Sub Worksheet_Change(ByVal c As Range)
If c.Address = "$I$3" Then
Select Case c
Case "": Rows.Hidden = False
Case 2: Rows("4:5").Hidden = False
Case 3: Rows("4:6").Hidden = False
Case 4: Rows("4:7").Hidden = False
Case 5: Rows("4:8").Hidden = False
' à compléter...
End Select
c.Select
End If
End Sub