Charge 1 time for product setup

I need to charge an $18 screen fee on T-shirts if the user purchases less than 24 of them. If they purchase 24 or more then there is no screen fee. I added it as a radio button 1 value attribute but it charges the screen fee on each size shirt, not just one time for the product type. Ideally the fee needs to go away when 24 shirts are ordered, but I can live with the screen fee if it only charges it once when t-shirts are ordered regardless of what sizes, colors, etc. Because right now if I purchase a Medium Black shirt, I get the screen fee, but then purchase a Small Black shirt, it charges the screen fee again.

Likewise, I have a few products that I get from an out of town wholesaler so I have a set shipping fee from them whether I order 1 item or 100 items. I need to pass this shipping fee onto the purchaser only when they order one of these out of town products. So I again have the issue of needing to charge them a one time fee whether they order 1 or 100 of these items, and only these items (so I can't simply add that shipping amount into the shipping cost because that would charge that amount on any order even ones without the out of town products).

I hope this is clear enough.
Thanks!