Changing Desktops as per typed in URL

Hi Experts,

I am having a requirement where for one portal I have two URLS. Now I have to display different portal desktops for each of these urls. I have tried using URL Alias option of Master rule collection. But its not working. Can anybody please guide me to know whether this is possible or not.. and if yes then how?

What am trying is

if typed url = http://portal1.com

then open portal desktop 1

else if typed url = http://portal2.com

then open portal desktop 2

please help. Its a bit urgent for me.

thanks in advance.

shubhadip