ASP.net call javascript then return a value to code behind

[Aaron873]

Hey all I am designing a website in ASP.net from a PHP designed site. They do their form checks via javascript and then submit all data via ajax if it passes validation.Is it possible to fire off a pieice of javascript from a submit button via code behind and read the returned value before i process to either postback to save the data or do nothing until the user corrects the fields indicated by the javascript?Thanks!