If you are using Standard Costs and/or Standard Price in The Business Edge for your pricing there is an easy way to change the Standard cost on a product from within a Purchase Order.
After you select a product code in the detail lines of Purchase Orders there is an option on the right-hand side under Additional Information for Standard Costs
The Enter & Edit Product-Standard Info screen will allow you to change the Standard Cost or Standard Price in the master file of the Product without leaving the Purchase Order