Add weight to Order and Delivery note

Hi! I need to add information about weight of items and total weight in Order (SO-) and Delivery note (DN-) as this is essential to calculate the shipping costs. I used ‘customize form’ to edit delivery note, but the total weight is not calculated. All I got from support that I need to make a custom script… But I’m not a programmer. Is here anyone who can help to customize in that way?