Adding a row in a table of a protected form

We have a new form with 2 sections: The first half has tabbed text fields,
radio buttons, and drop-downs; the 2nd section has a table with 2 header
rows, a sample row for data entry and 2 empty rows to start to fill in. At
the bottom of the second section there is a set of 3 text entry fields.
When we protect the form with both sections, it protects the whole table. If
we protect only the 1st section, then the tabbing between fields stops in
section 1 - you can enter in the table, but tabbing on the last cell of the
last row does not create a new blank row (you have to highlight a cell and
insert a row).
We want to be able to have the users add rows to the table as they need to
and still protect the other sections. How can we do this?
Thanks!