What i want to do is dificult to explain so i'll try making a scheme.

A B C D M N
1 9:30 12:00 Ponta 2:30 8:00 16:00
2 21:00 0:00 Cheias 0:00
3 07:00 09:30 Cheias 1:30
4 0:00 07:00 Vazias 0:00

I table ABC i count many periods of the day in wich i call in cell C the
name i want to other mission, in cell D i count the hours that period M:N
shows that are in period A:B.
I've made this formula but isn't working well, and also i'm having trouble
in counting 0:00 (24:00), example of line 1.

=IF($A1>N1;0;IF(AND($A1>$M1;$N$1>=$B1);B1-A1;IF(AND($A1>$M1;$N$1=<$B1;$A1>$M1);N1-A1;IF(AND($A1<$M1;$N$1>=$B1;B1>M1);B1-M1;IF(B1<M1);0))))

Understand what i a'm trying to do?
tks