PtComboBox focus problem

Hello,
I’ve create an application using Photon. This app is a form wich contains
PtText and PtComboBox. I’ve made a navigation system wich permits to give
the focus to each item of my form.
enter ou arrow down give the focus to the next item in the form
arrow up gives focus to the previous item in the form

When i give the focus to a text item everithing is well, but when i give the
focus to a ComboBox, the list is open if i use an arrow key to give the
focus, and it remidns closed if the focus is given by pressing enter (or
tab). I think this is default behaviour of the ComboBox to be open when an
arrow key is pressed.
I would like the combobox to stay closed even if i give the focus to it
using an arrow key.

Thx a lot for your answers.