[TYPO3-commerce] Problems with delivery cost calculation

[Tobias Ronsdorf]

Hi,

I got a couple of problems when trying to write an extension which 
calculates the delivery costs based on carrier, total weight, country 
and zip code. I tried to use the hook in 
class.tx_commerce_articlehooks.php but it seems that I can alter the 
price of the delivery but the value is not transferred to the next page 
although the variable is referenced.

Is there a better hook or a better way for calculating the delivery costs?

Is there a variable with the total weight?
I can get the values of the attibutes from the flexform, but I don't 
know which key the actual weight is.

Thanks in advance.

Tobias