More brain bashing

1) Create a form in Open Office Writer with a few form fields and an
embedded table that does a simple calculation of A1+A2 and assigns
the result to A3.  Protect the table except for A1 so that
you can change the value when not in design mode. Test it to make sure
it is working.

2) Export the document as PDF.

The resulting form will let you edit the form fields, but not the value
for A1.

I assume this is by design and that Adobe has no functionality for
making the calculation.  Is this a correct assumption?

Why would I want to do this?
I have created a form for a company that does some basic
calculations like this.  However not every user has Oo, and
the form looks like rubbish when converted to .doc format.
Adobe is ubiquitous at this company and the resulting export from
Oo looks excellent in Adobe.  That's why I was trying this.
It does however at this point look like it is not doable in this