gridviewrow operation

Hi,

  I have a gridview which consists of 25 rows. In gridview, I have radiobuttonlist and textbox. In

  radiobuttonlist, i  have  3 radio buttons named paid, not paid and exempted. default "not paid" radio

  button is selected.

              Here my problem is when i click on  "paid" radiobutton, the adjacent textbox should be enabled

 and again when I  click on  "not paid" radio button the data in the textbox should become blank and

 should disable so that no one  can edit  the textbox. This operations should be done on each and

 every row in the gridview.

           I am unable do this operations on one particular row in the gridview.