There is no setting for this and the post back is required so the two controls can exchange the information. If you do not want to have this, you can try using a custom layout for the editing form - either by using an alternative form or fully custom aspx page ("Editing pages settings" properties and you will set your custom page here) and use Ajax Update panel there or, the recommended solution would be creating a custom form control - this custom control will consist of multiple checkboxes and in the selection changed events you will be handling the behavior you want.