I have a speadsheet containing customer order details. If a customer orders
10 of one item and 5 of another item, I enter 10 in the column of the first
item, and 5 in the column of the second item...etc

I would like to be able to work out the total cost of the items in another
column automatically. Normally I would do £4.50 x 10 if a customer wanted 10
of an item, and so on manually until I had their grand total.
Is there anyway I can do this automatically?

Something like: SUM (IF cell A1 contains any value multiply by £4.50 (IF B1
contains any value multiply by £7.50...)) and so on across the speadsheet.

Could I also put the item costs elsewhere in the speadsheet to make it
easier it update price changes?

Many thanks for any suggestions/help :) Jess