Formula:

VLOOKUP (lookup_value, table_array, col_indenum, [range_lookup])

Step 1: First create two sheet “Price List” and “Sales Order” as below

Step 2: Now select cell on “Sales Order” where we apply VLOOKUP formula and give lookup_value index as below image

Now give the table_array value as below image

Put the comma after table_array parameter and give the col_indenum. Here col_indenum  is 2, and set [range_lookup] as false. Hence whole formula is

=VLOOKUP (C9,'Price List'!C9:E16,2,FALSE)

Now press enter button and see output

Step 3: Now apply all cell of column “Item Name”.

Step 4: Apply same process for display “Unit Price” as below image, formula for unit price as following

=VLOOKUP (C9,'Price List'!C9:E16,3,FALSE)

Step 5: Now you can calculate “Total” amount and percentage and whole output screen as below. Get the help for calculating sum, product and percentage from following link.

http://www.mindstick.com/Articles/e790a001-fcca-4077-bdbe-66da92bcc5fb/?Sum%20Function%20in%20Excel

http://www.mindstick.com/Articles/2820228e-d10a-438e-808d-00879cce50a3/?How%20to%20do%20percentages%20in%20Excel