How to achieve the use case in Portlet/Suitelet?

Hi all,

I'm looking for advice on the best way to achieve this use case:

* There is a field on a Job record that may contain some value

* A Portlet reads this value and conditionally displays some content

* If the value is null, I want to present a text input box right there inside the Portlet so the user can enter a value and save it in-situ

* Once the data has been saved, automatically refresh the Portlet so it displays new content

I can do pretty much everything above apart from the automatic portlet refresh. My Portlet embeds a Suitelet in a hidden iframe. The Suitelet receives the changed data and saves to the Job record. But, being a Suitelet, it does not have access to the N/portlet module, so cannot call refresh() directly.