Hi,
No, the PIX cannot do this (and you cannot configure it as you've seen). The problem we run into is on the outbound connections. If you have two translations built for an internal server on port 80, how does the PIX know which global address to translate the source address to? Address A or Address B? If we translate the response to an address that the client did not use when sending the initial packet, he is going to discard the response based on the fact that he got a response from someone that he didn't send anything to. You will need to configure your web servers to listen on different ports (80 and 8080 as an example) and then build your statics like this:
static (inside,outside) tcp host 1.1.1.1 80 host 10.1.1.1 80
static (inside,outside) tcp host 1.1.1.2 8080 host 10.1.1.1 8080
Hope this helps.
Scott