Inventory on hand margin

I am performing a calcuation to determine what the profitability on an item is at the time of sale. However, to do this accurately, I really need to use the average cost of the item on hand, not the purchase price.

The problem is, you cannot reference 'total value' of an item (i am guessing because it is calculated) nor can you access the average costing fields, that must exist somewhere if the item is costing type average. I have not tested FIFO or LIFO yet, but I am sure they are the same.

My alternative solution was to use the last purchase price from a sales order for that item, which, according to the documentation should be the item purchase price if the purchase price is not on the item and the item does not have a preferred supplier. However, when you do a new purchase order, it selects the first purchase price. I have raised a case for this.