invoice & emails

Hi,
We are a magazine company.
Our invoice manager asked me if it's possible to add an extra rule to an invoice:

situaion
client orders a couple of magazines these will fit through a normal mailbox. 380 x 265 x 32 mm.
I know a that I can put restrictions on the payment/shipping and shopping methode. I need to set a restriction on the volume,
if the volume becomes larger that 380 x 265 x 32 mm then it must become another payment/shipping methode and become a postal package. and an amount(4,60) will be added to the price.

question 1 : this is automatically done though if the shipping methodes are setup correctly?
question 2 : The amount 4,60 will this become an extra rule on the invoice?
If not what's the methode of adding an extra rule on the invoice?
question3: in the restriction input field. What is the correct way to but this: 380 x 265 x 32 mm restriction in.
Do I have to do it like this:380 x 265 x 32 or like this 38026532 or doesn't it matter. because when is use , . it coverts.


Ronald