How can I update date and time in a running presentation

Hi all!

I have a small slideshow with 5 slides.
On my backgroundslide I have a clock- and datefield set to variable.

The problem is that the clock just updates when I start presentation, and it shows the same time as long as I run the presentation.

I want it to uppdate at least after 60 sec.

Best regards
Niklas Engvall
Education for Adults
Borlänge, Sweden