I think you want this:
(A2-A1)+(A4-A3)
After you can format the cell "[hh]:mm"


"LMC" escreveu na mensagem
...
Hello Everyone,
Can someone help me on this (I think little) problem?
I now that my demand has been n demanded times and every time that we need
something, it's impossible to find the right information on the net so my
question is:

I would like to calculate the time between an arrival and departure in 24h
format for my work.

Example : Cell A1 arrival 9:30h, Cell A2 departure 12:30h, Cell A3 arrival
13:30h, Cell A4 departure 18:45h

Thanks for the answer

LMC