[ RESOLU par Lone-wolf ] : CommandButton Annuel

Option Explicit
Private Sub CommandButton1_Click()
Dim dt As Date, dt2 As Date

dt = DateSerial(2017, 1, 1)
dt2 = DateSerial(Day(Now), Month(Now), Year(Now))
TextBox3.Value = (TextBox1.Value) * (TextBox2.Value)
If Year(dt) = Year(dt2) + 1 Then
CommandButton1.Enabled = True
Else
CommandButton1.Enabled = False
End If
End Sub

Private Sub TextBox2_Exit(ByVal Cancel As MSForms.ReturnBoolean)
CommandButton1.Enabled = True
End Sub

Private Sub UserForm_Initialize()
CommandButton1.Enabled = False
End Sub