Not the best of solutions, but you can add a ComboBox to your form (which looks like a DTPicker) and hide the DTPicker behind it. You would want to make the heights the same but unfortunately the only way to change the height of a ComboBox is to change its font and/or point size, so you'll need to experiment to get its height to be equal to the DTPicker height. Once having done, set Combo1.Visible=False, and put the following in your form's Load event.
Code:
Combo1.Left = DTPicker1.Left
Combo1.Width = DTPicker1.Width
Combo1.Top = DTPicker1.Top
Combo1.Enabled = False
Combo1.Text = ""
Combo1.Visible = True