Deduct delivery fee before adding Sales tax

I have a form here:
http://remingtontopsoil.com/order-online

I recently added this code to automatically add VA sales tax to my order:
http://pastie.org/2102201

This code works. However the sales tax should not be charged on the delivery fee.

So the tax is calculated like this:
return total + (total * 0.05);

Is there a way to identify the delivery fee field on my form, so that I can subtract it from the total before applying the sales tax? The field label on my form is "Delivery Fee by Zip Code". Would I use the field name or is there a way to get the field "id"?

So can I change the code to something like this?
return total - delivery fee by zip code;
return total + (total * 0.05);
return total + delivery fee by zip code;

David,

Okay added this code, no JS error. Testing it on this page:
http://remingtontopsoil.com/order-online

I select a product and enter a quantity, the Order Total reflects the correct amount including the sales tax. But when I go to the bottom, and select the delivery fee from the drop-down, it's not added to the Order Total.

Here is my code:

var deliveryFee = jQuery('#input_2_20').val().split('|')[1];
total -= deliveryFee;

return total + (total * 0.05);
}

AWESOME...that did it!!!

Thank you very much. Great support with quick turn-around.

Hi Reminginton,

You would need to apply the same concept used to subtract the delivery fee from in the javascript to the code run in the gform_product_info_57 hook. The delivery fee should be part of the $product_info array.

David,

I figured this out. Thanks again for all your help.

I reword it. I want to add a discount or tax just to a price-option if a special product is chosen.

How can I achieve that?