Shipping costs not working out as they should

Hi (again)

Well I have product(A) and product(B)
Product(A) needs a delivery charge of £7
Product(B) needs a delivery charge of 99pence
However if Product(B) is purchased at the same time as Product(A) then I need to subject the shipping cost of 99pence from the order.

I have tried so many different variations and I just cannot get it to play nicely. Whats happening is the calculations seem to be backwards.

current my first shipping rule is from an example on this forum as I needed the functionality:
pickup -> IF Session variable pickup !=1 AND Based on session variable value IF the value of the Session variable pickup is != a value of 1 FLAT RATE of £7

(the above works)

But I need to include the Flat rate of 0.99 if the product is a certain type (ie vouchers that the website sells only charges 0.99 for shipping) I have used the column WEIGHT in my database as I dont require it for this online store so figured to use it to store either a 1 or a 0 to determine if the shipping costs should be excluded. (I set 1 for selling vouchers) so I can use this value in my shipping calculations. but I just cannot seem to get it working correctly.

any ideas from what i described? What sore of shipping rules should I be using?