Sorry for my english. Not native.
My solution isn't perfect, but it works quite well in our enviroment and I hope it work for you too.
First of all, I suppose both DNS points to the same IP.
Then you create a new website, in the same port (usually 80) and edit it to receive "only" members.example.com users (Binding option).
That site will be only show to users using members... (and invisible to the rest)
Inside it, a simple html page like this:
<!-- window.location = "http://www.example.com/members.aspx" //-->
</script> </head> <body></body> </html>
Save it like "index.html" and configure the site to use it as default web page.
Each time a user goes to members... will be instant-trasnfered to the page of ur choice.
The beaty of this system is that you can use the same method to move from HTTP to HTTPS and be transparent to the user.
Hope this helps.