Automatic Insertion and Addition in datagridView Columns

Question

Sir, I am doing a ADO.NET Project at the moment.

take a look to the form frmPurchaseDetails:-



You can see the ProductName  column is being filled in frm_Load Event.

the very next column PurchaseRate is to be filled as per the selection of products.

before going to the task, take a look the form  frmProduct where the product Name come from:-



You can see Product Name and Purchase Rate column.


I want also increment of TotalAmount column ( purchase Rate * quantity - Discount=Total Amount)

here is the form to be look like:-




So please help me on this topic