Hi Ambesh,
If your item is exciseable then first you need to set his assessable value into Item master or manual into marketing documents for that item from which excise will be calculated.
Excise amount will calculate from Assessable value only (Hope your tax formula is correctly created for excise).
So first, you need to create PO --> GRPO --> Incoming excise Invoice --> AP Invoice
then, SO --> Delivery --> Outgoing excise invoice --> AR Invoice
In above stages you will have different Unit price for AP and AR but same assessable value as far as my knowledge about excise is correct. Hence you will pass you excise in AR exactly as it is in AP invoice.
Hope it is clear to you. Let me know if you required more info.
Thanks,
Harshal