Can someone please help me with a formula?

I am working on creating an order form. The client has an ID Code and I have
already calculated the discounts each client can receive. The ID Codes are
alphabetical.

All the data is stored on one worksheet and I want the cell on the new
worksheet to show how much discount they will receive, eg 5%, 10%.

Furthermore, I need to calculate the discount from the sub total to give a
grand total.

EG.

Data to retrieve:

A4 G4
VIP Code Discount
BARAN 12%


Thanks in advance for your assistance.

Marty