This was a new discovery for me. I mostly work on web applications, but the last week, I've been working in the Client exclusively.
When changing a setting on a combobox, I caught sight of the above setting, "Run Exiting/OnChange events after value change". This little gem changes the behavior of comboboxes, checkboxes and radiobuttons, so that the OnChange/Exiting events fires immediately after the user has changed the value, instead of having to wait until the field loses focus.
The setting is a per field setting, so you can mix and match according to your needs.