Times and midnight issues

My problem is that I have a target time of 23:00 and I need to calculate how many minutes the actual time is late or early.

For the early I’m happy to get a zero output if minuses cannot be displayed.

The problem is that the actual time could be before the target time or after and also going past midnight.

I can get to zero or a calculated time even if passing midnight but as soon as the actual time is 1hr before the target time I get 23 hours and it needs to be either minus or zero.

=B2-A2+(A2>B2) [this works fine until the actual time is before the target time]

Anyone help please, and an explanation if possible of the work around.

Bslob

If 11PM is in A1, this will return the difference between the time in B1 and 11PM

=B1-A1+(B1-A1<-0.5)

with the custom format of [m]
12:02 AM returns 62
10:45 PM returns -15