I have three tables:

Table 1: Invoices
Table 2: Invoice Items
Table 3: Prices

My grid structure is as follows:
Master Grid is Invoices: when I click on invoiceID it will send the InvoiceID to Subgrid to view the invoice Items (Which contains the following: (Item No., Item Description, Quantity, Price and Shipping_Fees).
The Item_Description, Price and Tax are defined in Table Prices.

The master grid and subgrid are working fine.

What I am trying to do is to apply fill_form in the subgrid
1: When edit the Item_Description (Choose from the list) the Price and Shipping_Fees should changed automatically.
2: When add a new Invoice Item: Item_Description (Choose from the list) the Price and Shipping_Fees should filled automatically.

Is it possible and how can I achieve this.

Your kindly reply is highly appreciated.

Azhar