virtual ip with http host detection?

Hi,

can you point me into the right steps how to implement the following: internet -> webserver1.intra.myintradomain.com -> goes to: 10.0.1.150:80

internet -> webserver2.intra.myintra.domain.com -> goes to: 10.0.1.160:80

So I would like to implement above. I know how to just map all traffic from an external port (let's say 80) to ONE SAME internal host, let's say: 10.0.1.200.

But how do I map traffic analyzing the FQDN (webserver1. etc...) to an internal ip? I don't have such an option unter Policy&Objects/VirtualIP's.

Thank you.