Calcul de la valeur de plusieurs textbox

Private Sub t1_AfterUpdate()
Call ValeurTextBox(t1)
Call Total
End Sub
Private Sub t2_AfterUpdate()
Call ValeurTextBox(t2)
Call Total
End Sub
Private Sub t3_AfterUpdate()
Call ValeurTextBox(t3)
Call Total
End Sub
Private Sub t4_AfterUpdate()
Call ValeurTextBox(t4)
Call Total
End Sub

Private Sub ValeurTextBox(ByRef TB As IMdcText)
If InStr(1, TB, ":") = 0 Or Not IsDate(TB) Then
  MsgBox "Veuillez saisir l'heure au format 00:00"
  TB = ""
  Exit Sub
End If
TB = Format(TB, "hh:mm")
End Sub

Private Sub Total()
Dim D As Date
Dim Jour&
If t1 <> "" Then D = D + CDate(t1)
If t2 <> "" Then D = D + CDate(t2)
If t3 <> "" Then D = D + CDate(t3)
If t4 <> "" Then D = D + CDate(t4)
If CDbl(D) < 1 Then
  Me.Label3 = Format(CStr(D), "hh:mm")
Else
  Jour& = Application.WorksheetFunction.RoundDown(CDbl(D), 0)
  Me.Label3 = Jour& & "j - " & Format(CStr(D), "hh:mm")
End If
End Sub