Queries :: Rolling 12 Month Query - Keeping Track Of Orders Placed For Given Part Number By Month

I am trying to create a database that will keep track of the orders placed for a given part number by month. Currently, my table houses the part number, and the ordered amount for the past three years by month (there are thirty-five columns for every part). My column headings are ORDER_MAY_2013, etc. I would like to set a query up that will look at the column headings and pull the amounts ordered for each part for the past twelve months. In other words, I have three years of data in my table. In my query, I just want one year. However, I don't want to have to rewrite the query every month so that it will pick up the new data. Is there a way to accomplish this?

Is there a better way to build this database? I thought about just have four columns in my table - PART_NUMBER, ORDER_MONTH, ORDER_YEAR, ORDER_AMOUNT. The only problem there, is that every part (there are about 450 parts) would have to be listed 35+ times. That seemed too redundant to me, so I built the table this way. However, now I am having trouble querying against it.