TextBox au format date

Private Sub Textbox51_KeyPress(ByVal KeyAscii As MSForms.ReturnInteger)
    TextBox51.MaxLength = 10
    Select Case KeyAscii
        Case 46, 48 To 57
            ' 01/04/2016
            VT = Len(TextBox51)
            If VT = 2 Or VT = 5 Then TextBox51 = TextBox51 & "/"
        Case Else
            KeyAscii = 0
            MsgBox "Only numbers allowed"
    End Select
End Sub

Dim jourS As String, moisS As String, anneeS As String, dateTextBox As String
If Len(dateTextBox) = 10 Then ' Donc jj/mm/aaaa
    jourS = Mid(dateTextBox, 1, 2) 'Permet de séparer ta chaine de caractère
    moisS = Mid(dateTextBox, 4, 2)
    anneeS = Mid(dateTextBox, 7, 4)
End If

'Et après il faut poser tes conditions pour vérifier que la date est bien la bonne par rapport au mois et à l'année en cours :D
'Il doit cependant exister une méthode plus rapide et plus intelligente mais elle fonctionne !

'Constante séparateur de date
Public Const SEP_DATE As String = "/"

Public Sub Format_Date(cTBx As MSForms.TextBox, KC As MSForms.ReturnInteger)
Dim ici As Byte, flt As String, cr As String, drf As String, dtt As String

    flt = "##" & SEP_DATE & "##" & SEP_DATE & "####"
    drf = "31" & SEP_DATE & "12" & SEP_DATE & "2000"
    With cTBx
        ici = .SelStart
        If KC = 46 And .SelText = Mid(.Text, ici + 1) Then
            .Text = Left(.Text, ici)
            If Len(.Text) = 2 Or Len(.Text) = 5 Then .Text = Left(.Text, Len(.Text) - 1)
            KC = 0: Exit Sub
        End If
        If ici < Len(.Text) Then .SelStart = Len(.Text): KC = 0: Exit Sub
        If KC = 8 Then
            If ici = 3 Or ici = 6 Then .Text = Left(.Text, Len(.Text) - 1)
            Exit Sub
        End If
        If KC = 37 And ici = 0 Then
            If IsDate(.Tag) Then .Text = .Tag: KC = 0: Exit Sub
        End If
        If KC > 95 Then cr = Chr(KC - 48)
        If ici = 3 Then Mid(drf, 1, 5) = IIf(cr = "0", "00" & SEP_DATE & "01", "00" & SEP_DATE & "02")
        dtt = .Text & cr & Mid(drf, ici + 2)
        If KC = 32 Then
            If ici = 0 Or ici = 3 Or ici = 6 Or ici = 8 Then
                Dim voir As String
                voir = .Text & Mid(Format(Date, "dd" & SEP_DATE & "mm" & SEP_DATE & "yyyy"), ici + 1)
                If IsDate(voir) Then .Text = voir
            End If
            KC = 0:   Exit Sub
        End If
        If ici <> 8 Then
            If Not IsDate(dtt) Or Not dtt Like flt Then KC = 0: Exit Sub
        Else
            If Not IsNumeric(cr) Then KC = 0: Exit Sub
        End If
        Select Case ici
            Case 1, 4
                If ici = 4 And Val(Mid(.Text, ici, 1) & cr) > 12 Then KC = 0: Exit Sub
                If ici = 4 Then
                    .Text = Left(dtt, Len(.Text & cr)) & SEP_DATE: KC = 0
                Else
                    .Text = Left(dtt, Len(.Text & cr)) & SEP_DATE: KC = 0
                End If
            Case 3
                If cr > "1" Then KC = 0
        End Select
    End With
    Application.CutCopyMode = True
End Sub

Private Sub TextBox1_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
    Format_Date TextBox1, KeyCode
End Sub