Optimal method to write code to make fields read only depending on a check box

Dear All,

What is the best method to use to make fields read-only in Customer creation UI depending on a custom check box provided on the UI. The fields should become read-only/editable as on when the check box is checked/in-checked without clicking on the CHECK button etc..

Any information would be sincerely appreciated.

Thanks & Regards,

Tushar.