"Add more values" and triggered rules

I am using CCK to build a form containing a multigroup (which has a date field and a select listbox for choosing a location).

I have set up some rules that trigger when the date or location select fields inside the multigroup change, and they appear to be working fine. However, I expected that these rules would also fire if "add more values" was checked and another set of fields was generated/filled in (i.e. customer chooses to add an additional date or location), but this does not appear to be the case.

Is this behavior by design? If so, is there something like a multigroup token (or alternately some PHP logic) that I can use to set up an action for when "add more values" is chosen?