No, you can't. But you can manage focus, and draw whatever you want, or change state of your UI component. It's a good practice for UI components create several states: normal, highlited, selected, disabled and manage them with disabled system focusRect.
myComponent.addEventListener(FocusEvent.FOCUS_IN, onFocusIn);
myComponent.addEventListener(FocusEvent.FOCUS_OUT, onFocusOut);