dynamic form rule issue

What field type is the one that does not work to trigger the form rule?

The field that works and the one that doesn't are both formula texts fields.

Ah I added the triggering field into the form and it works. Does that mean that the field I'm using to trigger the condition has to be shown in the form? It was designed to be more of a field used in the background that's never shown. Is there a way to achieve that?

In my experience the form is lazy (ie for perfomance reasons) and does not recalculate fields unless it needs them for the form.  It would be nice if the form realized that a field was used in a form rule and hence included it in fields it recalculates when the data changes.

I typically have a section on the form called "Req'd for form rules" and then a rule like when some field is not equal to 99999999999, then hide section Reqd for form rules.

That way the form will "see" any changes to those fields in that section as data entry changes and the form rule will work, yet not expose those fields to users.

that worked! thank you