Force Numbers to Calculate

Hi, I've noticed that a Numbers spreadsheet does not calculate when it becomes the focus spreadsheet.

I have a formula which relies on Today() but it does not work unless I change something to make it calculate.

The spreadsheet does calculate upon opening, from closed, but often the spreadsheet stays open.

Is there a shortcut, a way to make Numbers calculate on demand, like the F9 in Excel?

Thank you for your help.