On Preload
The actions that will be performed right after the dialog is created in memory, before the dialog (or any of the objects on it) is shown.
You can use this event to set the initial visibility of each object on the dialog. Simply show or hide the objects according to whether they should start out visible or hidden. (By doing so before the dialog is displayed, you can avoid any visible "flickering" as the objects are hidden or shown.)
Note: Some actions (especially object-related actions) may not work properly on this event because it occurs before any of the dialog's objects are "created." If an action doesn't work at On Preload, try it at On Show instead.