Can I lock certain fields and leave others editable?

I'm attempting to build an invoice/credit card authorization form all in 1. The tricky part is that the form is actually both for me to fill in, and for my client. In other words, I have the form set up to do a whole bunch of calculations to keep me from having to do math. So, I'll fill in the items that are ordered and the quantities, while the form does the rest of the calculations. But then at the bottom of the form I have fields that I will need the client to fill in once I've sent it to them (credit card info, shipping address, etc). Is there any way that the client can fill in those bottom fields, without being able to edit the top fields, like the total cost?

Ideally, after I input my portion, everything that I entered and that Acrobat calculated as a result would become a locked item of the PDF, just like any other un-editable text on the page... leaving only those remaining fields for the customer to fill out.

Any ideas? Thanks!

(I'm on Acrobat Pro 9o on a Mac)...