[development] ajax in drupal module

Hi, I am working in drupal 6, and developing small module. I want to use ajax in a formAPI for a particular division to use separate add, delete functionality without the whole page refresh. I was trying to get solution from internet but i could not implement it. it was giving error or i could not understand where the error is. Please help me by giving any small example module so that i can understand and implement it. I am new for drupal. Thank you jayakumar