Maybe the description of the problem is not what it should be but let me describe my problem.
I want to add products to an order.
I have an order table with customer_ID, product_ID , Quantity, Unit_Price fields
I also have a product table with Product_ID, Product_Description, Unit_Price , and Stock_Quantity
When I enter a Product_ID (combobox) in my order tabel I want to copy the Unit_Price from the product table into the Unit_Price field in the order table.
What is the best way to do this ?