Need help Subtracting hours and minutes

Being a real novice I need some help in what you all would consider basics. I will try to explain what I am trying to accomplish. Basically I am trying establish time elapsed in different machine operator functions. I have starting times and completion time of the process in hours and minutes. In A1 I have start time 9:00, in B1 I have complete time 2:00. Naturally I have to subtract times to get the difference in hours and minutes and show in C1.
To slightly complicate things, there are interruptions that cannot be included in the answer such as breaks and lunch. Fortunately there are only three cases.
If Break time 10:00 - 10:15 ignore
If Lunch time 12:00 - 12:30 ignore
If Break time 2:00 - 2:15 ignore

So I don't get screwed up what format do I use.

Thank you for your help and understanding, I warned you I was a novice.

If there are other questions I can help with please let me know. I have read about adding .mm or *24 to the formula and things like that but I am totally confused.