Excise assessable value is not defaulting from assessable price list

Hi,

We have a requirement where bill to & ship to customers are different. Excise is to be calculated on assessable price list. We have created assessable price list & added in customer additional information of ship to customer. But, system is not changing assessable price as per the assessable price list. If we add the same assessable price list in customer additional information of bill to customer's null site, then there is no problem. If bill to & ship to customer is same, then also this functionality works. But, for different bill to & ship to customer, it is not