Tax on Freight

Please help me on Pricing Issue..

We have configured a Pricing Procedure where

{(Price - Discount + Excise Duties) + CST } + Freight = Total price and

{(Price - Discount + Excise Duties) + Freight } + VAT = Total price

i.e there should not be CST on Freight for inter-state customer , but VAT will be applicable on Freight for Intra-State.

When creating the Sales order, its not working. \

CST gets calculated on Freight as well.

Thanks in Advance

Sudip Sinha