eBay - how to adjust postage costs?

I usually state that if a person buys 1 - 3 DVD's or Games (both are the same size) the postage stays at a flat rate $5.00 ($7.00 express postage) and if they buy 4 or more, then the postage is $8.80 ($9.90 express postage).

Just wondering if there is any way to set it up so eBay automatically adds this up by itself so I don't have to manually invoice my customers rather than having them sending me rude messages about me trying to trick them with postage when they go to checkout.

Best thing if you want to do it like that is to change your shipping to a cost for each additional item.
Put your shipping at $5.00 for the first item and something like $1.00 for each additional item. Make sure this is in your listing.

Lets say you want to charge only $1.00 for each additional item.

Go into 'MyEbay/Preferences/shipping and discounts/ Offer shipping discounts on combined purchases'

Click on edit.
Make sure that
Allow buyers to send a single, combined payment for items purchased within the following time period''' Is checked
Make sure that
Apply a shipping discount when a buyer purchases more than one item from me. '''''' Is checked

Then click on
Charge my highest shipping cost for the first item and deduct US $4.00 from the shipping cost of each additional item.

Deducting $4.00 will make sure that each additional movie is charged only $1.00 off of your original shipping costs.

I sell dvd movies as well but I do not list shipping at all. The shipping details are in my Auction. Yes occasionally I get 1 person that moans about shipping fees. But they are easily put in thier place when I tell them that if they actually read the auction details then they would have known :D

I also add ' Your bid states you have read this auction fully and agree to sellers bidding terms' in my auctions

Hope this helps

I got tired of crazy emails about me overcharging on shipping and went to FREE SHIPPING for awhile and did ok as i raised prices and alot people bought more dvds as they felt they were getting something for FREE .GOOD LUCK!!!