correcting and average cost

How can I correct an average cost that has been received many times at the wrong cost? I tried taking inventory down to 0 then doing a positve adjustment at the correct cost, but average did not change much.

We use the Advanced Distribution add on so assuming AD this is way we do - If it is only the last shipment received into stock then we do a Purchase Cr/Adj Notes and EXACTLY reverse out the shipment using the same wrong costings. Then create a new purchase order and receive the goods again this time at the correct cost. If this is an item with many transactions then Item Journal the inventory to 0 on hand at the correct value. Run the Inventory Periodic activities - both Adjust Cost and Post Inventory Cost. Now create a new Purchase Order and receive the stock at the correct Unit (Average) Cost. There will be a need to journal off any purchase costs associated. Another more direct method that works under certain circumstances (have not be able to define the boundary conditions) is to - - run the Inventory Periodic Activities - journal off all stock on hand from all locations at the correct value - run the Inventory Periodic Activities - update the average cost directly on the item card - run the Inventory Periodic Activities - journal the stock back in at the correct value