Salut caje17,
Private Sub ComboBox1_Change()
'
dap = ComboBox1.Text
Me.ComboBox1.Text = Format(CDate(Me.ComboBox1.Text), "dd/mm/yyyy")
Me.TextBox21.Text = Worksheets("top").Rows(1).Find(what:=CDate(Me.ComboBox1.Text), lookat:=xlWhole, LookIn:=xlValues, searchdirection:=xlNext).Offset(11, 0)
...
A+