I've been struggling with this form for our business on and off for the past few months between other projects. The problem is this: I used check boxes to pick what shipping method to use (Ground, 2nd Day, Next Day Air). The first time you pick a shipping method, it calculates fine. If you change your mind and go with another method, you end up with NO shipping charge, or various other combinations of the 3. I know the first problem is the "ShippingCharge" being added as a SUM, however no other calculations I have found have worked. I have linked to our website the two forms that you can file > save as (identical, except one sells the product at $699 and one is for $799).
Any help would be great. You can also directly email me at: firstname.lastname@example.org
You need to learn how the various form fields work and how ther interact with each other.
For radio buttons and check boxes you can make them an exclusionary group, that is only one item of the group can be checked, so one could not select multiple shipping methods. You have to set the export value for each individual item, widget, to a unique value within the group.
If you carefully observe the results of changing the shipping method selection, you will note that the calculated value is using the value for a previous selection, so it appears the calculation order is not in the correct order. You will need to "Forms => Edit => Edit in Acrobat" then edit "Forms => Edit Fields => Set Field Calculation Order..." and move the fields up or down to sequence the fields in the proper calculation order.