Private Sub CommandButton1_Click()
Dim n As Long, a As Range, b As Range
With Sheets("Base")
n = .Range("A65536").End(xlUp).Row
Set a = .Range("A2" & ":A" & n).Find(What:=TextBox1, LookIn:=xlValues, LookAt:=xlWhole)
Set b = .Range("B2" & ":B" & n).Find(What:=TextBox2, LookIn:=xlValues, LookAt:=xlWhole)
If Not a Is Nothing Or Not b Is Nothing Then
MsgBox ("Impossible d'enregistrer plusieurs fois les mêmes données.")
Else
.Range("A" & n + 1) = TextBox1.Value
.Range("B" & n + 1) = TextBox2.Value
End If
End With
End Sub