There are different ways to change the price of an order, depending on how many items you ordered on the order number, and whether or not the order has been printed yet. For example, if there was an order with five items on it, you would have to follow a different course of action to that which you'd need if the order had only one item on it, and this in turn would be different to the process if you had raised the order but not had it printed.
When an order is raised, the status is usually set to P (as discussed in "How to raise an Order"), to indicate that the order should be printed that night. When the order is printed, it is passed among the system from one program to another, so that the second program can take care of the order, making sure its details are adjusted with each delivery and so on. The program which does all this is called POMAINT, and is accessed through Promis. If you don't set the status to P then it remains set to H for hold, and consequently stays held in whichever program it was raised - typically POGO or POGEN. If the order remains held in POGO or POGEN you can, almost by definition, change the price before it is printed.
If the order hasn't been printed yet, see here. Otherwise, you need to follow the instructions below. First find out the order number with the price you wish to change.
POMAINTfrom the Purchasing Menu
"WOULD YOU LIKE TO CHANGE THE PRICE FOR MULTIPLE ITEMS FOR THIS PART? (Y/N):"enter in the number of the item that you wish to change again. If you want to change the price of all the items (e.g. multiple deliveries of the same part, enter Y