Subtracting time for lunch from hours worked

I am using MS Access 2007.  I have a start field and a stop field and a
lunch 
field.
Start field and stop field are set up as short time (military).  Lunch is 
set up a a number.  Currently I am getting the minutes worked by using
this 
formula Minutes: DateDiff("n",[Begin],[End])

Then I take the lunch field and calculate it using this formula Expr1: 
[Service]![Lunch]*60

Then to get the total minutes I use this formula Expr2: [Minutes]-[Expr1]

To get the total hours worked I use this formula Expr3: [Expr2]/60

Is there an easier way to do this?

Thanks