automatic time formula

I am trying to find the way to get a formula that will give me the time updating the time just like a clock. then, i want to find another formula that by substracting the actual time minus the 23:59 will give me the housr remaining for that day.

example

actual time total hours in a day hours remaining
17:00 24 6.59 hours
=now() 24 =[now()]- 24
I did try this and many other ways but with no nosuccess. also the now() does not changes automatically. what am I doing wrong or not doing that this formulations dont work?
could you please help

Thank you
Ignacio