I'd like to add a button to a standard form (a sales order for example) that would just invoke a js function.  What I want to do is let the user kick off a function that totals up the weight and case count for all the line items.  It's not such a good idea to do it too frequently as we some times have orders with 50+ line items.

Is this possible, and if so is there any example code around?

Thanks!