I have an issue with a form that needs at least one field informed for sending it. The form is builded with some fields and a button that start an activity for searching.
In the begining, I thought to validate this sending the value of the fields to his temporal page (using Post Value on change) and, after that, applying a when rule to able/disable the button, but it didn't work.
This is another way to do it, but I want to avoid Refresh actions; even it is better to validate it in server-side, due to you only have to refresh once the activity has redirected you again to the form view. If you put it a refresh action per field in the form, you will be refreshing once for each field.