Custom Javascript snippet for PDF form

This should be failry straightforward. My client has a PDF form that makes a few calculations based upon the price of selling a home, and what it cost to build. In two fields, a calculation is made, and if the calculation is not between 2 certain values, it needs to bring up an error message and allow them to input a correct number in those calculated fields. ## Deliverables None of the contents in the pdf are to be distributed, shown or used under any circumstance. Complete ownership and distribution copyrights to all work purchased. I will send the pdf when bid upon.