I'm thinking of including an hour-tracking formula that will calculate hours worked.
I agree with Nomie regarding checking the archives. Speaking specifically to the formula you mention, I use the below formula for weekly time logs.
=IF(A1<>"",MROUND((B1-A1)*24,0.25),"")
What this does is it will round you to the nearest quarter hour, where cell A1 contains starting time and B1 contains finishing time. This will round to the
nearest quarter hour; e.g. 9:07am is rounded to 9:00 am, while 9:08 will be rounded up to 9:15. I am not sure how you'd keep time for AEA actors, but it's likely that you'd need to always round up, e.g. if your rehearsal is 9:00-10:00, and you go over into 10:02, you'd need to round up to a 1/4 hour instead of leaving it at 10:00. For that, you would use the CEILING function with the formula below.
=IF(A1<>"",CEILING((B1-A1)*24,0.25),"")
If I'm totally missing the mark, ignore my post - but these are some formulas I use to convert time into 1/4 hour increments, so working for 1:15 becomes 1.25 hours. Once the time is converted it becomes much easier to manipulate into whatever other math you need to do.