how to update dynamicaly generated gridview textboxes

Question

i have done to create the parent textbox and child gridview dynamicaly add row in child and all the data is save..... but now i want to update all the data against the Purchase order number and all data must be papolate in specific text boxes like parent txtboxes and gridview dynamicaly (generate gridview textboxes agains the purchase order number) generated textboxe and then update that rows