I have a wordpress site that currently only allows users to post a price of their item. I need them to be able to have that "base price" but also have a quantity box next to the price field that whatever value they enter in that box will then multiply with the price and give a total cost of the order. So right now, let's say an item costs $5. The seller posts that item and lists the price for $5. If a buyer chooses to buy it, the total charged will be $5. But if the buyer wanted to buy 10 of them, I need them to be able to input 10 in a quantity box which will then multiply with the $5 base price and show $50 as the total to be charged. All I would need is the quantity box beside the price field, and a button that says "Calculate Order". Whatever the number that comes from the "calculate order" button should then be reflected when they click "Purchase Now".