I would be grateful if someone could help me with this:

I often have the need to show the elapsed time between two cells where cell
one has say 22:30 and cell two has 04:30 (which would be the time the next
morning). Imagine a car starting it's journey at 22:30 and reaching it's
destination 6 hours later. It's easy if the times are on the same day but go
past midnight and I find it impossible so have to take my socks off to do
the calculation.

Following that (and here imagine lots of car journeys) I then have a
problem summing all of the outputs if I want to show the hours or minutes
total of many calculations, say 73 hours or 4380 minutes. I've tried
customising formats but so far all my fiddling about with combinations of hh
or mm or even mn have proved fruitless.

Hopefully some kind person can give me a nudge in the right direction.

Regards ..................... John