about locking and unlocking the tables

Hi,

I have 2  winforms containing same set of controls (whose values will be stored into the single table say userinfo in mysql db) to which two different persons  have access,but I want to avoid the access to the  forms by two persons at a time.i.e., if person A is editing the form the table has to be locked and the person B is able to edit the form only after the table is unlocked by the person A. Inorder to that I have to lock and unlock the tables how to achieve this? (code used: C#)