How to Add a Sub Form to track Expenses

[serviceenvoy]

I have a need to add a sub form to track expenses into a form that is
for work orders.
I need to track expenses by the following criteria:
-Whether it is labor or parts & give me a total expense for each
-Who is to be reimbursed for it (Repair Center, Technician,
Manufacturer, Wholesaler, etc.)
-What the total expenses are for the call
-A way to notate individual actions on each line item in the expense
subform (charged to credit card, entered in accounting, sent check,
etc.)

I'm pretty sure I know how to add a subform, I just don't know how to
setup the subform with all the criteria I need and do the calculations
correctly. I hope I have given enough information to explain what I
need.