[Scribus] PDF Form calculations

[Thomas Worthington]

Hi.
   Very simple request: I need a PDF for which takes a price entered in one  
field, multiplies by 3, checks a button to see if VAT is to be added at  
17.5% and if so adds it to the total, then sets a second read-only field  
to the result.

I've tried all sorts of things in the custom calculation but I can only  
get the AFSIMPLE_CALCULATION function to work and that's not adequate.

This is so trivial compared to some PDFs I've seen and used that it must  
be doable, but how? Where does the code, in particular the "IF button  
pressed" part, go?

Thanks,

Thomas Worthington