Yeah follows regular order of operations. I have a pair of extra parantheses above just to make it easier to read, so you can ignore that.
Also, you need to use (23-varH) otherwise you'll end up with 25hr days. Try it with 22:30... if you use 24 for the number of hours, the result will 2.5hrs until midnight
You can always do use Message() to display the current value of variables for testing and troubleshooting, something like Message("hours= " & varH) or even Message(TimeStamp()) !!