Pricing Doubt

Dear Guru's

I have a situation,

scenario 1,

Material A sold at base price - Excise has to be calculated on Base price.

Scenario 2

Material B sold at base price but has an 62% abatement on MRP value and the excise has to calculate on the abatement value and total will be base price + excise calculated on Abatement.

If i want a single pricing procedure can it be maintained.item level or item based calculation. Is it possible and if so how can i acheive it

regards,

R.Sudhir