Adding formula to Entire Column

I am working a spread sheet that has two columns. Column A has prices, Column B calculates the change in prices of column A. So each cell in column B contains a forumla that calculates the change in price between the previous price in column A and the current price.

I need to calculate a large number or prices, so Is there a way to automatically, enter the formula into all of the cells in column B and make sure that that formula adjusts so each cell in B is calculating the change in price of the corresponding adjacent A cell?

Thanks!