Want to use AJAX Technology in Comment Posting

Hi all,
I want to develop a Plug-in for Word press that enables the user to make comments without refreshing or navigating to another page by using the AJAX Technology. I need a hook / Filter that I use to override the default behavior of the link for posting comments. Also I want to place my own code into the page that displays the comments.

Please tell me which hook / Filter /template that I have to capture / modify in action function.

Thanks in Advance

Best Regards,
Tariq Rahim