Auto Sum Formula Question

I have created a form with tables and form fields so that users can enter
their data by typing it in. The form can also be filled in manually.

At the bottom of the form I have a table w/ 4 colums for various fees. The
Auto Sum formula works great.

Here is the problem: 50% of the people who will use my form will simply
print it out and fill it in by hand. They will not be filling out
electronically.

When I print my form, the cells for "Total Fees" automatically populate
"$0.00". No data has been entered in the table and my guess is that the
formula thinks that "$0.00" has been input into these fields.

How do I make it so that the auto sum formula does not execute unless
someone enters data into the form fields w/in the table?