pricing MWST

hai sap gurus,

I want to calculate the tax ( MWST ) for the customer on price after the discounts and before the Fright is added how to make it possible. I am using pricing procedure RVAA01 i don't want to change the standard one.... is that possible.

Now the tax(MWST) is calucuated after the fright is added ... so i want that to happend before fright is added.

with regards

sashidhar