B4J Question Preset controls in a form

Hi, I would like to preset controls like radio buttons and labels from previously saved file in a separate modal settings form. I cannot put data to the fields before the settings form is opened and i cannot find an event like "on open form" to do it afterwards. If I start the form with show_and_wait, i cannot update the fields programmatically before the form is not closed again. Once again, help would be appreciated.
Georg