How to trigger update of calculated fields without changing attributes?

Hi there.

I have finally mastered calculated fields. Bascially I have an item with a due date. If the current date is past the due date, another field is set to "overdue" when any of the linked fields are altered. So far so good.

Now, I would like that field to turn "overdue" even if no attributes are changing, e.g. the item is not touched for a long time, obviously time is ticking and it becomes overdue.

Any idea how this can be achieved?

Regards

Franca