You can do that with web  services.
Search for the webservice behavior. This is a microsoft client side behavior (.htc file) which works on IE4+ only. You can call your webmethods from this component. It's very easy

some relevant links
msdn.microsoft.com/.../overview.asp
msdn.microsoft.com/.../using.asp
http://www.webreference.com/js/column99/index.html

And here is exactly what you want to implement
http://www.aspalliance.com/Yusuf/Article12.asp