Hi....
My one of client also want that scenario...that time i have make following changes...
U need not to create to excisable WH or Excisable Code or Excisable Tax Code
Simply you create a UDF on Batch ie you want to Purchase that items in Batches...On that batches you can put Excisable amount arrives during purchase and can passes that excise to Customer when you sell that item from that particular batch...
If you think this is ok for you then i can tell you further process in Details as i have created...
And if you want to purchase a Excisable item with non excisable tax code there is also a another process.....Which you want tell me i will explain to you in detail....
Regards,
Sandy