How can I create a cell format for time that will display hours, minutes and
seconds where hours may exceed 24 hours. I also want to suppress hours
and/or minutes when they are zero. For example, I want to show the following
times
28:09:30 06:15:47 00:52:34 00:00:12
as
28:09:30 6:15:47 52:34 0:12
preferably with a single custom format.

I have tried several times but have not been able to solve this.

Also, in the custom cell formats, just what do the characters [ ] and @
mean? And what are formats such as [-F400 ... ?

I really appreciate any help you can offer.