I build and sell computers on the side for some extra $

Every time someone wants a computer they have tell me what they want then I have too look up how much it will cost...etc

I would like to create some drop down boxes with different options to choose from. Then a review button to see what you chose and the price. Then a submit button to send in the request to me.

Well I know how to make drop down boxes (big deal) but I’m not sure on how to go about doing the rest. Any help would be appreciated.