I would like to create a "countdown clock" that reflects the number of
hours/minutes/seconds remaining for an employee to work based upon their
scheduled start/stop time. In cell A1, I have a TIME() formula that reflects
their start time, and in cell B1, the same formula reflects their stop
time---for example:

A1 B1
=TIME(7,0,0) =TIME(15,0,0)

In the above example, the start time equates to 7:00 am and the stop time is
3:00 pm. Ultimately, I would like to show the "time remaining" based upon
this work schedule on any given workday. I tried using a NOW() formula to
first establish the current date/time, and then subtract this from cell B1,
but all I get is ##### symbols. Can anyone help guide me?