I have tried various formats but cannot sum the following:-

B5=12:00:00 C5=14:00:00 D5=TEXT(C5-B5,"h:mm")=2:00
B6=18:19:20 C6=19:19:20 D6=TEXT(C6-B6,"h:mm")=1:00
B7=03:00:00 C7=21:00:00 D7=TEXT(C7-B7,"h:mm")=18:00
.. TOTAL D8=21:00 but what is the formula to
Sum D5:D7?

Thanks, Nosam (OldGiraffe).