how to get total amount in flexgrid

[jemz]

hello please help me on this how to get total in the flexgrid...example i input the item_no k0001 when i press enter key it will display on the grid the the item_name the item price etc.... and when i input on the txtorder_qty.text 5 it will display to grid the amount and when i input another item_no k0002 and when i input the txtorder_qty.text 3 it will display also the amount
and the last is to get the total amount how much will be the customer will pay all the item this will display to the lbltotalamount...thanks in advance... hoping for your positive responds