Shipping Flat Rate, need help with PHP

Hey everyone,

Just as a lot of other people I'm looking for the best way of shipping. In my clients store there are 2 categories, 1 has a shipping fee of 1,76 and one of 7,50 (larger items)

I've been browsing the forums and the most useful one was the weight method (also described in the help-section of zen-cart.com)

However, that would mean that about 2500 items have to be changed in order to make them all that shipping cost.
So, I think the following would be a good method, but since I'm not good at PHP, I really need some help.

1. I use the normal flat fee rate, (1,76) for the majority of the products
2. Next I would like to use the freeoptions-method (but make it 7,50) telling it to be an option when a specific weight is chosen
3. the larger items are given this weight
4. when multiple items are chosen (even mixed, because there usually lies the problem I've read on the forum) the rate stays at 7.50!

However, I don't want it to be a choice for the customer (they always choose the wrong one...:frusty:)
So, what i want to accomplish is that when the freeoptions-method applies, the flat rate choice is not shown.

I think the only way is through PHP, but I'm not sure..

Can anyone help me please?(and perhaps a lot of other people who would find this very useful)

Thanks a million in advance

Dimar

Almost forgot: I want it to NOT show this option when no bag (so no weight) has been chosen (just to make it a little more tricky)

Thanks again

Is it harder then I thought? If you don't know the 'solution' but see where the difficulties lie, please tell me so I can try and adress them.