Yes, I don't want to include the additional charge in the subtotal, you are right. This is because the subtotal, by definition as an invoice term, is the sum of the ordered products' cost and the additional charge amount does not refer to a 'real' product ordered. So, I would list it under the tax amount, as 'handling fee' or something like that.
I will take a look in the post you sent me. Thanks again for the input.
Any further comments regarding the above, especially for my previous
post in this thread (#3) would be welcome.