how show/hide panels before executing response.redirect

i have form kicks off response.redirect download record once complete. i also wish bury form arrangement 'thank you' quarrel before route takes place, however seems asp.net engine only does route but doing 2 tasks before following code:

if (success)
                {
                    lblsuccessmessage.text = _successmessage;
                    showmessage(true);                        
                }
                else
                {
                    lblsuccessmessage.text = _failuremessage;
                    showmessage(false);
                }

                if(success)
                    response.redirect(_downloadurl); 

any thought i force page transform before route kicks in??

thanks heaps
greg