Automatically update the time time difference

I am using this formula =(NOW()-A1) to see the time difference between a start time in cell A1 and current time using now(). I want to see the time updating automatically and showing the difference time.


For examle the time at cell A1 is 23:00:00 and if the current time in computer is 23:40:00 then the formula will give the result 0:41:00. however, to get the updated time I need to open the sheet or enter in the formula bar. But I want it to automatically update and show the time.

Try this solution

http://www.ozgrid.com/forum/showthread.php?t=67764