Publishing a script that displays and example input from the expression window of the publisher?

I'm working on a script that calculates the shipping cost of a package based on the weight of the package (as entered by the user in an input prompt). I want to publish as a PDF that calculates the cost at a weight that I enter in the expression window of the publishing editor, but no matter what format I use, the script doesn't utilize the input. How can I get the script to run using an example value for the package weight without removing the "input" prompt from the code?

[Matt Rulli]

weight = input(' Enter package weight [lbs]: ');

I want to keep this in my code, but I want it to display a computed value for a weight I enter in the expression window of the publisher. How do I bypass this portion of the code so my published PDF will display a price for an arbitrary weight entered in the expression window?