ASP.Net postback on link button click

I need to pos开发者_StackOverflowt data from my ASP.Net webform page to a 3rd party php site. As part of post data I need to send encrypted data containing timestamp. The timestamp needs to be generated when the link button is clicked and then request needs to be redirected to this 3rd part site using http post. I know PostBackUrl can be used but then I can not do server side logic before the post is done.

Is there an alternate way to postback using link button's onclick event?