Cell A1 ~ 09:00 (Plan arrival time)
Cell A2 ~ 09:15 (Actual Arrival Time)
Cell A3 ~ 0:15 (Late by 15Min)

The above tells the timing for arriving to work and schedule to arrive to
work. The calculation would be showing as such;
ABS(A2-A1)=A3

My problem is, how do we get a negative. for example if
Cell A1 ~ 09:00
Cell A2 ~ 08:55
This will tells that the arriving time is earlier by 5Min which should give
-5min. how do I get a formula for such?

Thanks in advance!