datagrid - Product code entry for billing

Question

 

 

I want  to add the product code in grid then  corresponding to its productname, uom , price it will automatically come in the row . the  we the qty.

 

or otehrwise the  barcode corresponding to itsproductname, uom , price it will automatically come in the row . the we the qty.

 

i need ur help ... how to validate the datagrid and how to load  data..