calculating time durations

Running Excel 2010
Our manufacturing process is start heating metal, stop heating metal, start pouring metal, stop pouring metal. For my purposes "stop heating" and "start pouring" are the same. So I have 3 time values to enter and I want 3 calculated time durations. Length of heating cycle, length of pouring cycle and time between last "stop pouring" to the next "start heating" cycle.
Raw data is manually entered into one sheet. It's only for me, so style/format doesn't matter. The duration can be displayed as minutes or decimal hours.
I tried several different ways to format the entered time values but the simple calculations for duration don't work. Right now the time values are formatted as numbers, which works just as well as anything else so far...
I'll be surprised if I have to apply a custom (if > 60 then -60) type of function but I can't find any canned formulas for getting these durations without the predictable time/number conversion problems. Likewise, I could convert from hours:minutes to hours.hours but do I really have to?
Thank you for your help.

I'm not sure but

=REPLACE(RIGHT("0000"&B7,4),3,,":")-REPLACE(RIGHT("0000"&B6,4),3,,":")

and [m] формат

Thank you BMV! I looked at the example and I will see what I can do to integrate this more fully. Much appreciated.

Hello protonLeah- Thank you for your reply. I use Excel often, but not in a very advanced way, so it's good to get this kind of information you are sending. I like the idea of best practices so I'll add the colon... The only bit I'll say about not using it is that I dislike data entry and always want to reduce keystrokes. 1234 on the number pad is quick. 12shift-colon34 takes longer and I make more mistakes. But if it supports better function later then I'll put them in now.
I'll work with that formula and your suggestion about date/time. Thanks again-