Stop a postback in javascript

Question

i have an ASP webform with a JQuery Thickbox, i have an image that opens the thickbox when user click.

once open the thickbox it shows me a grid with several rows an

Answer 1

hmmm let me try.. (i dont speak english and dont know the correct words to explain that i want but ill try :P)

i call a javascript __doPostBack BUT it takes too much to respond and stay in Loading... i want to stop the postback, something like a response.end but in javascript.

if my script takes too much to execute then call a StopPostBack or something..

thanks.