Pricing Condition determination based on Tax Code

Hi,

I am in a situation wherein I would like to determine a set of pricing conditions in a PO based on the tax code I use.

I tried using condition tables with field combinations such as company code-tax code, plant-tax code, etc., for my Access Seq.

On analysis of pricing procedure in the PO there is an error against my condition record "Access not made (initialized field)".

When creating the condition table using the taxcode field I encountered the below error:

Warning 859 Foreign key cannot be created for the selected field A980-MWSKZ

(A980 is my condition table)

Would appreciate quick help.

Thanks

Sameer