You can set up a custom order by using Order Fulfillment, which is a tool that allows you to create an order for any of your ads for any price and for any amount of time. It's super flexible and is the best way to create custom orders for your advertisers. To place an order using order fulfillment you would first go to the Orders section and once you're there you would then click the CREATE NEW ORDER button to start putting the order together.

You can change the price, the dates and the amount of impressions for the order and once you have it set up the way you wish, click the Create Order button and it will be set to run for the dates you specified.